i'm continually being told that my iCloud and me email addresses need fixing, but entering the addresses and the Apple password as authentication doesn't work.

This may be your problem, an updating setting problem. Apple is aware of the problem, but there is no definitive solution yet. I also have to warn you that I am not sure how the problem I am talking about translates into your Windows problem.

Note that some have solved the problem by signing out of iCloud, restarting their devices, and signing back in. 

In looking for something to help you, I suggest you use my search link https://www.google.com/search?client=safari&rls=en&q=update+apple+id+settings&ie=UTF-8&oe=UTF-8. You will see a number of links that may be related to your Windows problem. As indicated above, I have not seen a definitive solution for it though. 

If you want to contact Apple Support to deal with your problem, see:

Get a call from Apple support to help solve your problem using this link https://getsupport.apple.com/?caller=kbase&PGF=PGF63005&category_id=SC0245&symptom_id=23362

Apple ID Support https://support.apple.com/apple-id

Apple ID account security for country-specific and region-specific help https://support.apple.com/en-us/HT204169

Get Support: We’re here to help https://getsupport.apple.com/. Go through the options to find the best one.

You need to enable 2 Factor Authentication on your Apple ID and create an app specific password to use. If your account won’t allow 2 Factor Authentication, try 2 step verification.

Apple ID -Two-factor authentication          

 Two Factor Authentification availability.     

 Apple ID - Using app-specific passwords.     

Apple ID - Two Step Verifications FAQ    

Great. Be safe.

Easy fix.