To resolve this issue, follow these steps:
1. Open Jamf Pro Settings: Navigate to the settings in Jamf Pro.
2. Global Settings: Select "Global" from the settings menu.
3. Automated Device Enrollment: Click on "Automated Device Enrollment".
4. Check Last Sync: Look at the last sync time. It shouldn't be long.
5. Select Your ADE: Choose your Automated Device Enrollment instance.
6. Search for Device Click on the "Devices" tab and search for the device using its serial number.
This should help you determine whether the device is properly assigned and whether there's a synchronization issue.
If you have tried the above suggestions and still no joy, worth checking that the Mac is in the correct MDM Server in Apple Business Manager.
We have a few different MDM Servers in our ABM. The Macs also pitch up in a seperate MDM Server if they have been added to ABM via Apple Configurator.
@Hasibravo & @AitchKay
Guys, thanks for your suggestions. I tried all steps, but everything seems to be fine with the synchronization. Anyway, the newly assigned Mac does not appear in the list. I also checked the number of licenses and it's 250 in total. Only 209 licenses are in use, so I still have 41 licenses free. I also checked the MDM instance - we have only one instance, so it should not be a problem as well. I don't know what else to try. Our new MacBooks are added to ABM by our supplier. We don't add them manually.
Update: our IT Operations Manager has been able to correct this problem. The license file has been uploaded again and it started working correctly. The same license file... 
No changes in this license file. It's so strange...
Great!! Glad you got it working @DavidSpribe 👍
This happened again. 1 hour ago I have unassigned a serial number from MDM (this is needed to create a temporary account with admin privileges, in order to have Secure Token installed). Now I'm trying to assign that serial number to our MDM again, but it does not appear in the PreStage Enrollment database. What could be a problem? I have checked and the MDM server is synchronizing every 2 minutes with ABM.
It started happening about 2-3 weeks ago. Before, I never had problems with assigning and unassigning. I could unassign a device from MDM and assign it again after 15 minutes without a problem. Now it either takes too long (the time interval between unassign and assign should be about 24 hours), or it does not assign a serial number at all. Just would like to know, which side has the problem - ABM or MDM
