@Neil_Billingham, can you post a screenshot of what you are experiencing on the new PC? Is the PC onto which you are trying to logon your Roon Server or a Roon Remote? What is the error you are experiencing on your mobile device using ARC?
We’ve activated diagnostics to troubleshoot this issue and noticed that you’d recently signed into your account - I’m assuming that this issue has resolved itself in the interim? If not, please reach out in a new topic thread and we’ll happily pick up the trail. Thanks!