Today prime is only showing grey boxes. Amazon account is current and device is active. Using Roku TV Sharp Mobel: LC-50LB481U and Roku TV 5318x. All is up today.
I removed channel and reinstalled Prime.
All other channels working without issues. Netflix, britbox etc.
Router and modem have been power cycled.
Prime works on the computer without issue.
Just checked it on my Ultra 4670 and everything looks fine. When you removed the Prime channel, did you reboot the TV before installing again? And I don't mean just turning the TV off and on. You either need to use the system restart option in the menu or pull the power for 20 seconds or so.