RBR50 won’t accept new guest password

I’ve had a RBR50 Orbi with two RBS50 satellites for many years. Firmware version V2.7.4.24. The system has worked fine until yesterday when I changed the guest password. Since then no matter what password I enter, it drops the password for the guest network and leaves it unsecured (no password). I’ve tried again and again, with the same result. I’ve tried unplugging and plugging back in to reboot, no luck. Today I tried resetting (paper clip to push reset buttons, 10 sec hold) the router and both satellites, reinstalled everything, and still the same result. I’ve changed the guest password in the past without any problems. Now I cannot get it to accept a password for the guest network, no matter what I’ve tried. Anyone have an idea what is going on?