Since Sony are having difficulty solving this I’ve found a solution that doesn’t involve factory reset:

Go to “settings” (e.g. Home button then settings)

“Set Up” > scroll down to “Customer Support” > scroll down to “initialize personal information”

This will reset and log you out of all your accounts (but keep picture settings). 

Youtube will I’ll work again after sign in. You will also have to sign back into Netflix and amazon. But otherwise everything else should work fine after that. 

The “initialise personal information” might be in a different place depending on your tv - so search around your settings if you can’t find it. 

Otherwise try reseting cookies in your opera browser app.