This error is being returned by HMRC. Have you linked your QuickFile and HMRC accounts? Have you also received confirmation from HMRC regarding your MTD enrolment? If so, when did you receive this?
thank you for getting back to me so quickly, i think i fixed it, i submitted my first return before quickfile and HMRC were linked which caused the error, i could then not submit another return until i clicked the revoke VAT return and then submitted it again sucessfully. thank you