I understand how important it is to have your VAT submissions working seamlessly, Splanton. I suggest clearing your browser's cache and disconnecting the MTD connection so you can submit your VAT form in QuickBooks Online (QBO).

It seems the connection between QBO and HMRC needs to be refreshed, as this often resolves connectivity issues.

Here's how to disconnect your QuickBooks from MTD:

1. Go to the Gear icon, then select Account and settings.
2. Open the Advanced tab and locate Making Tax Digital.
3. Select Learn how to disconnect, then click Continue.
4. Confirm by selecting Disconnect, then return to QuickBooks.

After disconnecting, let's proceed by clearing your browser's cache and removing any temporary files that may have caused the issue.

Once you've cleared the cache, you can reconnect QuickBooks to HMRC by following the steps you used previously. For reference and guidance, here's an article for you to follow: Set up MTD (Making Tax Digital) for VAT in QuickBooks.

If you still encounter errors, don’t hesitate to reply. We’ll be here to assist you.