We have more than 900 iOS devices enrolled on MDM protal. In last month mdm profile for all devices changed to "Not verified". Due to this we are unable to publish apps on iOS devies. All commnds remains in pending states. I did some research on it, everyone is saying to reenroll the device which we really don't want to... Any help would be really appreciated...
What Settings is showing there isn't a provisioning profile of the app but the trust of the certificate that signed the MDM enrollment profile. The only way to change that would be to update or reinstall the MDM enrollment profile or determine what's failing in chaining the signing certificate to a trusted root certificate (you can guess which is usually easier).
That said, the MDM profile not being verified shouldn't have any impact on the MDM channel. Are you sure you weren't affected by some bug like updating iOS via MDM with JAMF?
Certainly sounds like your push notification certificate may have expired. Depending on where they were purchased and how you enrolled them will determine what you have to do to get things back in order. In most cases you will have no choice but to wipe them and start over.
In Jamf Pro check: Settings > Global Management > Push Certificates and note the expiration date. If it's a past date then you're looking at a wipe and enroll. If it's a future date then something else is causing this. When where these iPads enrolled?