I have a Linksys WRT1200AC running OpenWrt 21.02.1. I haven't been able to change the router's IP address and the DHCP range. I want the router IP address 192.168.2.4, and the DHCP range to be 192.168.2.13 to 192.168.2.230. But when I try to make those changes, the router keeps going back to default 192.168.1.1 and 192.168.1.x IP range. I've tried hitting apply save and save and apply, as well as hard rebooting after saving and applying.
My changes, starting with a default openwrt router:
Network > Interfaces > LAN 
IPv4 address changed from default <192.168.1.1> to <192.168.2.4>
Under DHCP Tab > General Setup, changed Start to 9 and Limit to 230.
Here's screen shot (nope, can't post images)
After making those changes, I hit save and then save and apply, I get this countdown.
 can't post images, ugh!
"applying configuration changes..."
When the count down completes, I get the
"Failed to confirm apply within 90s, waiting for roll back"
I noticed my computer's network interface disconnect and reconnect, but doing ipconfig shows I still have the old 192.168.1.x IP address, and the router is still at 192.168.1.1 instead of 192.168.2.4.
Edit: It's so confusing. The web interface, after I go back to accessing it on 192.168.1.1, still shows the 192.168.2.4 edits. It's like it retains the changes I wanted to make, but is not using the configuration that's being shown on the UI. It's using the configuration that was previously there, now no longer shown.