Hi!
As far as i know, if there havent been any updates since my last try, the only option is to reset the ipads via Apple Configurator 2 (where you can bulk reset devices) and then run the setup assistant again, we had to put them in DFU (service) mode for this to work.
The thing is (if i remember correctly) that its during the assistant that a token gets created for the DEP and that is whats controlling the certificates and so on. This is not a limitation in Meraki MDM, but just how the DEP works. Please anyone correct me if im wrong but this was the case last summer when i had this exact problem.
If your users are comfortable with it they can actually start the process themselves via iTunes on their computers and re-enroll with their accounts, this makes the step with Apple Configurator unnecessary.