I have an installation (albeit not working at the min) on windows 10. Just installed on Mac, asked me to update computer ID in the store, what does this mean? Does this mean I can only use my license on one machine, or do I just change the computer ID again when I open the software in Windows 10 and using it on more than one machine I own is fine?

Hi,
http://www.esenthel.com/?id=doc#License_Keys
You can use it on 1 machine at a time, so you can just switch back the Computer ID after switching to another machine.

Many thanks, sorry for all the questions.