Welcome to Roku Community.
Thanks for letting us know about the issue you are experiencing accessing the Disney Plus and Prime Video channels. Aside from the said channels, does the issue only occur on these specific channels or all channels on your Roku device? Did you restart your Roku device before re-installing the channel?
That step is crucial when performing troubleshooting. If you haven't tried the suggested order (remove > restart > re-install), we would recommend giving it a shot once again. We also suggest doing the restart from the Settings menu by navigating to Settings > System > Power (If you do not see a Power submenu, skip to the next step.) > System restart.
Let us know if there's any difference after.