Older iPad will not accept valid Network Password

I have an older iPad, possibly Gen 2 or 3, that we pulled out of a drawer and have been trying to get it connected to our T-Mobile 5G modem/router without success. The network displays in the list of available networks and after carefully entering what I know to be the correct password, I always see the "unable to join" error message.

I've even gone so far as to use the DFU reset process by connecting the iPad to my MacBook and allowing a reset of the iPad to use the MacBook's Internet connection, which now had wiped all user apps and settings and brought it to the initial "Hello" setup screen.

I've triple checked the password and what I enter is correct. I read somewhere that unless the iPad has an IP address, it will not connect to a network but since it has been reset, I've got nowhere to go to get past the initial connecting to the Internet to continue the setup.

Could it be that the iPad is so old, a 5G signal is not compatible? I no longer have a 2G network running.

Thanks for any feedback.