Hi Jim,
I assume you're already checked your Android version (settings... about phone) and it's not 4.3 and baseband doesn't end with MJ9.
Bear in mind if you take the OTA it's possible your bootloader will be locked, making it harder to do that custom rom, if you choose to go that route again.
There are pre-rooted stock roms you could flash, O/W the option to flash the OTA will probably show up again in a few days to a week.
It's also possible if you factory reset, you might get the OTA. For most people, they have the best luck after an OTA by factory resetting anyway.