From time to time, the HMRC Making Tax Digital for VAT (MTD for VAT) system becomes unavailable - normally because maintenance is being performed or because there is an issue. This prevents Easy MTD retrieving your VAT information and submitting VAT returns. HMRC normally (but not always) publish the reason why their system is unavailable on the Making Tax Digital for VAT: service availability and issues page of their website.
This website can be conveniently accessed in Easy MTD by clicking the Service Availability option in the Value Added Tax section of Easy MTD.