Phone saying incorrect WiFi password when it's correct

Have you rebooted the router? That is one of the first things to try. Let us know if it helps; either way I will explain why later.

"...I also cannot 'share' the password from another device; when we try to do that, the phone that we are trying to share the password from says 'Password not shared - there was a prob..."

Is that even a thing? Why you do that?

Hard reset the router

peter_watt wrote:

"...I also cannot 'share' the password from another device; when we try to do that, the phone that we are trying to share the password from says 'Password not shared - there was a prob..."

Is that even a thing? Why you do that?

It is a thing. Apple devices that share an Apple ID also share Wi-Fi passwords. So if you enter the password on one device it will propagate to the others.

If the router has taken umbrage with that particular phone the best thing is as Lawrence suggested reboot the router or as I suggested hard reset the router.

Also restart the phone and then Settings, General, reset, reset network settings

Lawrence I must admit none of my devices have ever shared wifi passwords despite them showing in my keychain.

Maybe I need to set it up but I never saw the need!