wifi connected but network unavailable

My Roku Express 3930X is receiving network error codes (such as 003 and 014) despite connectivity. It started about a week ago. I have tried everything I can think of. I have tried:

Checking connection
Set up connection 
Resetting the router/modem (everything else in the house is connected. I have 2.4 and 5 GHz capability with both illuminated.)
Unplugging and restarting router/modem
Unplugging the Roku and reconnecting after 30 seconds
System update
Network connection reset 
System reset
Factory reset

After the factory reset, it failed to authenticate for a while because the email wouldn't send and then the screen wouldn't refresh. It finally went through.

I set up my Netflix login. Afterward, clicking the Netflix icon takes me to a blank black screen.

Amazon sign-in worked at first but now produces an error message.

AppleTV gave error codes about connectivity until suddenly working. And then not working again.

Roku help says my device is not supported for calling in.

At this point, my Roku is an unreliable, unusable paperweight. Ideas appreciated.