I have completed the MTD for my VAT return but cant connect to HMRC.

Hi DavidB1947, thanks for joining the Community

Please try connecting by going to the Account & settings > Advanced > MTD > Learn how to connect and follow the on-screen flow. 

If you continue to reach a discontinued page, contact our support team directly by chat or clicking the Help icon in your QuickBooks account. Our agents available here will have access to set up a remote screen share to check this further. For more details on how to reach them, click this link: How to get help with QuickBooks.