I have been advised that there is a delay with HMRC with getting the MTD set up finalised. If you have had your confirmation email from them and are still seeing this error then you will need to contact the VAT helpline.
I registered for MTD about a month ago but only linked it to QuickFile yesterday, I read somewhere about waiting 72 hours. I will also try again tomorrow and see if I get any luck. Thanks Simon
Have you registered for MTD with HMRC? If so, when did you do this and have you received a confirmation email?
We have been informed by HMRC that there is a delay in sending the confirmation emails, and until these are received then you may see the error 500. During this time, they have advised not to contact the VAT helpline, nor try and submit a return, but wait a few days.
If you have received the confirmation email, waited 72 hours, and you are still seeing error 500, then I would advise to contact the VAT helpline.