RBR50: Orbi app returns "Unknown error." verifying security account.

I am posting an update to this problem for future reference and other users.

I did PM a moderator with details (as FURRYe38 suggests several times in this thread). The moderator helped me open a support case with Netgear and I spent several weeks working with Netgear by email and telephone trying several different solutions. Many of the solutions included these steps: back up my router configuration to a local file, do a factory reset and restore the configuration. In the end, we did not find a solution to the problem, and I bought a direct subscription to Bitdefender software so I would keep it running on my computers and phones. At this point, Netgear Armor is not running in my RBR50 router, and I'm OK with that.

I will point out several things: 1) FURRYe38 does provide good advice and pointers in this thread (thank you again FURRY). 2) Netgear support spent a lot of time working with me on this problem and would have worked it to resolution, but I gave up on it (because it wasn't worth my time any longer). 3) Everyone's individual router, account and email configuration is different, so don't be discouraged by the lack of a "common" solution to what seems like a "common" problem - if you are persistent (and specifically more persistent than I am) you can probably get this resolved for your specific configuration. 4) It's a good idea to learn how to back up your router configuration, do a factory reset and restore your configuration.