I am an administrator of the cellular device console in VMWare Airwatch however I have several cases where the registration has already been deleted from the administration, and on the device it does not allow us to uninstall the Intelligent Hub application, although it is not found enrolled.
This happens on a smartphone with an Android platform, when you try to configure it again with a new QR, it is detected as invalid, additionally the equipment does not allow us to execute reset to factory values, since the option is disabled.
They know how to uninstall the application without executing a reset or loading S.O
When your devices are no longer linked to Workspace one, you can hard reset you tab or phone on Android. Usually you have to turn off you phone then hold power and volume up or down. Google it to see the specific procedure depending on your manufacturer.
The other way is to use ADB command to factory reset it. You'll have to link your device with an USB cable, but you may have restricted the mechanism in restriction profile.
To get ADB (result from Google)
When you enroll the device again, you can remove it previous enrollment entry and the invitation if it's still recorded, sometimes it helps. I don't know what do you mean by "detected as invalid" do you have an error message ?