Devices will not connect to 5G -- password incorrect

[SteelersKPE]

When I try to connect different devices to the 5G network, I'm now getting the message either that it can't connect to that network or that the password is incorrect.

The password is not incorrect, it's the one I've been using for years. The router is not new. Some of the devices are new and some  are older. Here are a few of the things that I've done:

• I have reset the router
• I have asked devices to forget the 5g network

Customer service chat did not help. 

Thanks for any help you can provide.

[Cang_Household]

What kind of router do you have? A G1100?