My MTD VAT return has been rejected by HMRC. Message says contact HMRC with their error code. I do not have one. What is this code?

Hi mb86, thanks for joining us here on the Community - are there any other users with access to submit via MTD on the QuickBooks account? Usually, an error code would appear on the screen that you're seeing, to be quoted to HMRC who will be able to identify the exact issue. 🙂