For more information about that channel's features and functionality, you'll want to contact Amazon Prime Video Support to inquire further. Many channels on Roku are developed and maintained by the channel provider themselves.
Amazon has announced in emails to Roku owners that, effective November 1, 2021, their Prime Video will no longer support a number of older Roku models.
The model numbers affected are:
Roku 2 HD/XD/XS models 2050X, 2500X, 2720X, 3000X, 3100X Roku LT models 2400X, 2450X, 2700X Roku SE model 2710X Roku Streaming Stick models 3400X, 3420X, 3500X
(The Xs or other letters at the end of the model number are distribution codes and are irrelevant for this issue.)
To check your model number use Roku menu path Settings / System / About
Roku Community Streaming Expert I am not a Roku employee, only a user like you. Please, no support questions via private message -- post them publicly to the Community where others may benefit as well. If this post solves your problem please help others find this answer by clicking "Accept as Solution.".
Streaming Stick 4K+ 3821 | Streaming Stick+ 3810 | TCL Roku TV 43S245/C107X
Amazon Prime Video has been updated to support profiles.
Much like when Netflix added profiles, older Roku units don't have enough power to support them.
On November 1, 2021, Prime Video no longer works on: 3500X, 2710X, 2720X, 2700X, 3050X, 3100X, 2400X, 3000X, 2500X, 2450X, 3400X, and 3420X.
A quick look at the Roku Wikipedia article and the list of models suggests that the Broadcom processor based devices with a 600MHz or slower clock rate are the ones discontinued. The new code may just run too slow on that generation CPU.
All of the devices affected were released in 2013 or earlier. It's a good time to treat yourself to an upgrade.