I appreciate you checking in with us. You should be able to fix the application error message by disconnecting and reconnecting Making Tax Digital (MTD) in QuickBooks Online (QBO).
To disconnect the MTD option, follow these steps:
Click on the Gear icon.
Select Account and Settings.
Go to the Advanced tab.
Disconnect MTD by clicking on the pencil icon in the Making Tax Digital section.
Then, reconnect it by signing in to your HMRC account again.
Choose Done.
For further guidance, here's a great that article will provide more information:
You should be able to access the VAT section in QBO. Keep me posted if you have any questions. I'll get them answered.
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