If you purchased a Vimeo Producer or Premium membership via the Mevo iOS app and your account unexpectedly downgraded, you will need to manually download a new version of the Mevo app and re-upgrade.
The reason for this is we transferred ownership of the Mevo app from Vimeo to Mevo Inc., which caused any Vimeo memberships purchased via that app to no longer auto-renew. To resolve this, go to the App Store, download the new version, and re-upgrade your account via that app. This is also required in order to receive future updates and new features on the Mevo app.
Mevo provides more details in its help center.