You've imported your DEP token. Did you create an enrollment profile and reset the device to actually enroll it?
In the Intune portal, go to Devices > Enrollment > Apple tab (on right panel) > Enrollment program tokens > Click on your imported token > In the middle column, choose Profiles in the Manage section > Create profile button and choose iOS/iPadOS.
Complete the profile wizard. Set your options. Start without affinity to get the first one under your belt. Set Supervised to yes as the at is the goal of automated enrollment. I recommend locking the MDM profile to prevent users from unenrolling. Set the behavior of Setup Assistant (allow Location Services so time is set properly without user intervention). Review and Save the enrollment profile.
Now click on it again. The wizard does not allow device assignment until the profile is saved. Click on it and select Assign devices. Press the Add devices button to add your test units.
Optionally. Once you have the existing devices assigned, you can set the enrollment profile as a default. This will allow future assets to auto-associate.
Now that you have the enrollment profile created, erase the iPad and allow it to go through an automated enrollment. Basically, you will be asked for your language and country, be asked to put the device on a network, and then the next step should be to enroll. Once enrolled, the device(s) will appear in Intune.
Next steps are to create profiles to control device settings and service and then to import your VPP token and set up app policies. Intune is not the fastest MDM. Be patient. Things can take their sweet time.
Hope this helps. Test, test, and test some more so you understand the decisions you are making and the workflow.