I have a WNR2200 V1 with the Fimware 184.108.40.206 and can not Flash any OpenWRT Version over the Web ui. Even in the Recovery Mode i can send the File without errors but nothing happenend. Before i flashed DDWRT without any Problem and back to stock.
Do you have UART adapter? If you do, what do you see on the console when you try to flash it from web ui?
Can you provide complete bootlog (you can censor MAC address, but I want to see u-boot output and partition table)
Does your MAC address match backside label?
Can you provide output head -c 128 WNR2200-V220.127.116.11.img
Which is your current firmware or confirm that it's same as mine:
md5sum 64ffb77cf8b7da6ce75b4a53cfd9ffcb WNR2200-V18.104.22.168.img
I have tested flashing OpenWrt from this firmware, it worked for me. Maybe you have a different regional version?
Yes, this is reason why factory firmware does not accept the image. It has to contain exactly device:wnr2200 in the first line, and the checksum of complete image should be 0xFF. The checkum is just arithmetic sum of all bytes mod 256.
Try to get the snapshot from my link, it has correct header: