When submitting your VAT return under MTD you may get the following message:

'Unable to send request. Cannot open Internet connection. Unknown 12007'

This occurs if you've signed up with HMRC for Making Tax Digital (MTD) for VAT, but you're trying to submit your VAT Return through software that's not MTD compliant. 

1. Check that you've installed either Sage 50 Accounts or the Sage MTD Submissions Module.
2. Ensure you have the latest software updates installed.