Trouble adding v3 hub to existing setup with V2 hub

I have a smartthings environment already. It has a V2 hub. I recently bought some new First Alert smoke detectors (SMCO410) and could not get them to add. I read that they don’t play well with V2 hubs but work OK with V3 hubs. I have a V3 hub that was used at a different location. I’ve been trying to get it to add to my system. I’ve done the hard reset (hold reset the power on, wait for solid yellow and release reset). The hub shows up in the web console without a firmware version. My app sits at downloading updates. I pulled the power during the download phase and plugged it back in and the screen changed to a status bar. That got to 99% and eventually (several minutes) failed.

Is there a better process to get a new hub added to my smartthings environment?

if the V3 hub was not in use (Claimed to your account) since March 2025… then you are most likely experiencing a expired security certificate. Follow the troubleshooting guide in the following thread to resolve: Troubleshooting SmartThings Hub 2018 and Aeotec Hub