Unable to activate win 10

Just completed an unplanned reinstall of MacOS which included Parallels. didn't lose any data so thought good time to refresh win10pro install. I have a digital licence and I have done this before successfully (just using the install wizard)

Reinstall went perfectly but win10 won't activate:
First try via activation screen - Error code 0xc004C003 (apparently digital key invalid or blocked)

Then tried Trouble shoot >Changed hardware - Error code 0xd000000d and asks to verify if I have a connection to the internet (I have)

I have done this before an dit automatically activated. I really don't want to buy another licence... I did speak to the Indian call centre who assured me they could do nothing as they down support apple products - wouldn't answer questions about my account for anything... poor I thought.

So:
1. How do I find out which version of windows 10 I have a digital licence for (just incase wrong version installed...)?
2. How do I get around this issue?