Hello @ver89,
If you're referring to re-enrolling devices via DEP, you'll need to make sure that once you've removed and re-assigned those DEP settings to a device, that you then factory reset the device in order for the settings to be pushed and the device to complete enrollment. The DEP page should list the profile as "Pushed" and the Apple icon should go green once its checked into Dashboard.
After the enrollment has been completed, you should then be able to find the iPad under the devices list.
I'm sure you've come across this KB article already, and may be the one you're referencing, but I'll share it again for posterity as it is quite helpful:
https://documentation.meraki.com/SM/Device_Enrollment/Apple_Device_Enrollment_Program_(DEP)#Applying...