Have to sign in everyday to connect to the internet.

[#1]

It may be worth looking into the router logs to see if it's a loss of power, sync or authentication.

With regards to why it's asking for a password I'm not 100% sure. Is there any chance you can get a screenshot when this next happens?

[#2]

Is this a Plusnet remote configured device? Could there be an issue with that if it is?

[#3]

This is what my event log says, no idea what any of it means.