Hi Newbloke-42,
I think you have proven the OK button on the remote works by getting to the App you want to open, as it's a free app does the uTube app open, if it doesn't do you get an error message. If you go to diagnostics you can check your network connection which is required for the apps. If everything appears to be good try doing a factory reset of the box, just select the option to keep your recordings.
