What @stangri suggested will work, and the other two ways [there's four ways total to switch primary <-> alternate partitions] are listed in the WRT AC Series wiki under Firmware Recovery.
If you already know how to utilize putty, @alexmow's great info about switching via SSH will likely be the quickest way (see the SSH tab under Firmware Recovery), whereas the easiest, and most user friendly way is @stangri's suggestion to install the luci-app-advanced-reboot package.
You can see a step by step instruction for installing and utilizing the package in the LuCI tab under Firmware Recovery
You do not need to do anything any more, as the flashed factory firmware works. Stangri's advice was too late.
As you now have already flashed that OEM factory firmware, it is on the current partition. Right now you have the Openwrt firmware in the other partition (from which you flashed the current OEM one). JW0914's advice will help you to switch into the Openwrt partition, if you want.
Just remember that there are two partitions and you always flash from the current partition to the other one, and then booting switches automatically to that partition. So you always have the previous firmware still available in the other partition. That is the rare fallback feature found in the wrt1900ac series.
Wiki explains the ways (u-boot console, ssh console, power switch, advanced-reboot app) to switch partitions, but the wiki article is a bit cryptic as quite much information is hidden in fancy tabs.
I guess it takes roughly a bazillion more critisizing postings like these to wake up $someone and make him aware that perfect for one is not perfect for all.
The situation is like in a restaurant where you complain about the awful taste of the food, and the chef yells at you "How dare you to not like my food? I put all the spices in that I have in my kitchen, it MUST be good!!!11"
The good thing is: Contrary to a restaurant which is owned by one person, the OpenWrt wiki is from the community for the community, i.e. the community can influence the menu and the way the meals are cooked. If something is not to your taste, raise your hand and say out loud what is not optimal. Even better if you make a proposal on how to improve the meals: Take less salt, less curcuma, more ginger. You get my point.
wrt1900ac wiki is not the easiest one for newcomer. Some advice is formatted into tabs like I already said in my post above. I feel that would be simpler for the casual user to see all the available options right on the screen instead of having to navigate tab by tab e.g. through the partition switching options.
Similarly, the dual partition nature of wrt1900ac series and its implications/possibilities are not quite that clear to the newcomer. The dual-boot nature of dual firmware partitions is very rare and exists only in a few routers. Yes, most of the detailed information is scattered in the wiki (like in partition tables), but may not be quite easily understandable for casual users.
Like discussed far above, there was an earlier attempt by alexmov to write additions explaining things in a simple way, but that got quickly deleted due to redundancy. Key additions:
E.g. the use of "sysupgrade -F" options was described in that added text that got later deleted. (and this whole thread is roughly about that info not being easily found in the wiki)
Yes, wiki is a community effort, but we need to also allow others to add contributions, although they may seem redundant to specialists of a device.
Friends, I absolutely do not understand you, but I believe you
Do I have problems with a router or do I need to do something else?
Can I continue to flash it on DD-WRT via Web UI?
You clearly can't read... the WRT AC Series COMMUNITY decided on the formatting and layout, including utilizing the tabbox plugin. Yet again, you can't seem to be bothered to do your due diligence... but here, I'll make it easy for you..
That doesn't hold water... Tabs are specific to certain things, i.e. whatever is on the tab heading is what the tab is about. Stating that's difficult to comprehend is like saying a book's Table of Contents is difficult to comprehend. There's a ToC for a reason... it's right there to the right at the very top of the page, and if you're stating that's not the easiest, we clearly have different definitions of "not the easiest"...
See, all of this was already hashed out BY THE WRT AC SERIES COMMUNITY, but who cares about that right?
Change the wiki from what the Community decided they wanted it be and I will change it back. Like I said earlier: "What is getting old is having people who have no interest in contributing to the ToH criticizing the way the Community chose to have it formatted.
By all means though, since the facts don't seem to be sinking in, regardless of however many times I have to continually state them, why don't you PM @davidc502 to fact check the facts I keep repeatedly stating? I could provide other user names for the OpenWrt forum, but since that's dead in the water... perhaps you'd like to see the archived RSS feed posts I maintain in Outlook of the conversations regarding what to include, what not to include, why it should be formatted in the this way and not that way, what should the order of things be in the ToH, what should be closer to the top, what should be closer to the bottom, should this be worded that way or this way, etc.
Like I said, a years worth of discussions occurred regarding the content and formatting of that wiki, so instead of tearing down what the WRT AC Series Community created for the WRT AC Series ToH, perhaps one should be asking how can we better the ToH's of other devices. I only wish the communities surrounding other devices chose to dedicate even half of what we did to create a truly comprehensive wiki.
It's always been unfortunate that it appears I'm one of only a few who've actually taken the time to read through the DokuWiki plugins' pages prior to creating a wiki (evidenced by the formatting in majority of wikis), or while doing major edits to one.
Properly formatting a wiki takes time, so I understand why many don't... but to ostracize members who do is beyond asinine.
Beggars shouldn't be choosers, so when one finds a member who's willing to spend hundreds of hours (yes, hundreds) formatting wikis, perhaps it's not the most astute approach to continually attempt to ostracize them...
With that being said, tabboxes are not in line with the new wiki guidelines implemented a few months back.
When I've had time, I've been experimenting with different ways to format the additional content, as the purpose of tabboxes, or at least the purpose I utilize them for, is to streamline information in a clear left-to-right reading order that's natural to all but a few languages.
Tabboxes have always been a pro/con plugin, as while they allow a wiki to contain a massive amount of information while having a small footprint, inactive tabs cannot be printed in any form utilizing any browser extension that I've been able to find (I've tried 10+ thus far).
Perhaps @hnyman, @jeff, & @tmomas are willing to take the hours out of their days to re-format tab boxes into a more proficient way that's in line with the new guidelines, then test each change on both PC and mobile devices to ensure formatting stays cohesive and does not become discombobulated.
As I stated before, I've tried repeatedly, starting in 2016, asking other members to contribute to the ToH, and minus other members who help to maintain the ToH with up-to-date links, version numbers, etc. not a single person on this forum, or the OpenWrt forum before it crashed, ever chose to take up the offer. So unless any of you three are going to donate hours out of your days to help, perhaps all three of you should consider shutting it.
This is the last time I will address the ToH concerns any of you three bring up, as I've provided more than enough rationale and explanations to three people who have no interest in lifting a finger to help.
On the alternative partition.
Both OpenWrt and the OEM firmware use logic where the currently running firmware stays without changes as the fallback option, and the flashing is performed and the subsequent boot is done on the other partition.
LS, I'd like to point out if you're having trouble with OpenWrt that LEDE build you pointed out is extremely out of date. If you flash to the latest build of OpenWrt you will find it runs very well on the WRT3200ACM. Try Davidc502's build since OpenWrt 19.x never came out this year and hasn't officially been released in forever.
