It could be that the connection between your QuickBooks Online (QBO) and HMRC is no longer active, Tracey.
Connections automatically expire every 18 months to ensure security. For this, you can reauthorize the link.
Here's how:
- Log in to your QBO account.
- Navigate to the Taxes menu.
- Under the VAT tab, click Edit VAT, then Edit settings.

- From there, turn off MTD.

- Once done, click Save.
- After that, you can now reconnect your QuickBooks to HMRC using the correct MTD credentials.
If the issue persists even after reauthorizing the connection, I recommend contacting our Live Support team during their support hours. They can securely access your account and provide tailored assistance to resolve the problem promptly, ensuring you can file your return without further delays.
Feel free to reply to this thread if you need further assistance.