Hi there, Giles.

I appreciate you keeping us updated. And I can see the importance of accepting client invitations in QuickBooks Online (QBO).

It appears that you're encountering an error message when trying to accept an invite in QBO due to a regional restriction. This error typically occurs when attempting to connect to a client's QBO company from a different region. To get this fix, you may need to ensure that both you and your client are operating within the same region or jurisdiction as mentioned by my colleague ChristieAnn.

As for your concern, if those two companies need to be deleted and resubscribed, there's no need to do that as long as your clients are using the correct region for QBO. 

For future help, you can check out this article to help guide you in managing users: Add and manage users in QuickBooks Online.

If you have further questions about accepting a client invite, let me know by commenting below. I'll be here to lend a hand. Have a great day!