Sign in blocked on many apps

Why are many apps not allowing sign in? For example, Whatsapp is constantly "connecting", my bank card app stops at sign-in and goes no further - not even an error message. the apps behave as if they are not connected to network but I have 'reset network' and it did not fix the problem.

I can access the internet e.g. websites. Some of the apps report no network connection but it is connected. In all cases the app seems to fail to login to whatever account the app is related to.

Any ideas? Could I have accidentally switched of some permissions setting? It's has been doing this all day.