MTD - NOT_FOUND: The remote endpoint has indicated that no data can be found.

MTD - NOT_FOUND: The remote endpoint has indicated that no data can be found.

This message (in Aqilla) is coming from HMRC, not Aqilla:

In this context, it means that there are no liabilities in HMRC's MTD records for the company in question. You can ignore this message for liabilities and payments in MTD.

If you get this message for VAT Returns & Obligations you should contact HMRC in the first instance.