wrt1900acsV2 -Can't get back to OEM Firmware

I tried the turning it on and off multiple times.
I tried sysupgrade -F /tmp/wrt.img and other directories
Cannot get the oem img to flash from interface either.

What is the secret sauce?

Other topics say It is solved, but do not say how it was solved.

Appreciate help. Thanks

isn't it lower case f?
sysupgrade -f file

No.
-F and -f are different options.

-F is the "force" option in LEDE that should enable ignoring firmware image checksums and get OEM image accepted.

root@LEDE:~# sysupgrade
Usage: /sbin/sysupgrade [<upgrade-option>...] <image file or URL>
       /sbin/sysupgrade [-q] [-i] <backup-command> <file>

upgrade-option:
        -d <delay>   add a delay before rebooting
        -f <config>  restore configuration from .tar.gz (file or url)
        -i           interactive mode
        -c           attempt to preserve all changed files in /etc/
        -n           do not save configuration over reflash
        -p           do not attempt to restore the partition table after flash.
        -T | --test
                     Verify image and config .tar.gz but do not actually flash.
        -F | --force
                     Flash image even if image checks fail, this is dangerous!
        -q           less verbose
        -v           more verbose
        -h | --help  display this help

Still trying to learn how to return to original Linksys firmware from LEDE firmware.

Can't use lede flash or restore - nothing works.

Is LEDE a one way firmware? Kink of like the Hotel California - you can check in but you can never check out!

Is there no way to go back to Linksys?

What I really want is to use the Untangle.com image.

I go back and forth no problem.
WRT1900ACv1 and 2
WRT3200ACM

I use the below:

fw_setenv boot_part 1 ( or 2 depending)
reboot

If you got LEDE flashed on both partition, you won't notice that you forced a boot the other partition because they will both be booting LEDE...

Display your current boot partition issuing fw_printenv boot_part, use @mojolacerator commands, then once rebooted if nothing seems to have changed issue again fw_printenv boot_part to confirm that you are on the other boot partition.