Currently On iPhone remote 1390 and server 1392. Shows update available in remote but when click on install shows downloading progress bar but never progresses and after a second or two says error checking for an update. All else works fine, internet fine, updated many times. Tried first rebooting the Nucleus + and didn’t change anything. All fine in the web admin web interface.
Wonder if the servers are overloaded or the update was pulled.
To confirm, did you completely power down the device? Do this again, but this time leave it unplugged for a few minutes before rebooting. I’d give your router a reboot as well, and see if you’re able to update.