Let me share some details about why you're getting this message, PFCEng.
Issues like this happen when QuickBooks isn't authorised. You might want to check the confirmation email from HMRC and verify if you can start submitting VAT returns. This usually arrives within 24 to 72 hours and will contain your new MTD credentials.
If you don't see an email, check the spam/junk folder, or contact HMRC if you still haven't received it. Once you have the MTD credentials, proceed and follow the steps below.
For the complete guide, you can browse this article: Take action status when connecting to HMRC for MTD. There are some tips you can try to get your QuickBooks back on track.
If you're still unable to connect to HMRC, I recommend contacting our QuickBooks Online Live Team. They can take some account-specific info to check the reason for the failed connection.
When you make a VAT payment to HMRC, or receive a refund from them, you need to record all VAT payments and refunds before matching them with the associated bank transactions in QuickBooks.
I hope this clears out some of your worries today. Please consider posting here again if you have other questions. I'm always around to help you @PFCEng.