Error message "Maximum number of managed device reached" after upgrading Panorama to 10.1.8

• After upgrade Panorama from 10.1.x to 10.1.8, licensed-device-capacity reduced to 25, The pre upgrade licensed-device-capacity was 100
• Commit push to devices failed with the below error:

Validation Error:
mgt-config -> devices -> <serial number> constraints failed : Maximum number of managed devices reached
mgt-config -> devices is invalid

• Any Panorama
• PAN-OS Upgrade 10.1.x and 10.1.8
• License keys

• There are multiple device management license keys on the Panorama. 
• When multiple license keys exist for the same feature and their expiration dates are 'never', but issue dates are different condition check fails with logic error.
• That causes configd process choosing the oldest key file and prevents commit push to devices due to > 25 managed devices

1. This is a known issue reported in PAN-208537 and the target fix versions are 10.1.9, 10.2.4, 11.0.1
2. The workaround is deleting the older existing device management license key from Panorama CLI (Note: The Tab key can be used to auto-complete the file name):

> delete license key <license-name-key>

• Then re-fetch the licenses (or retrieve licenses from the server on WebUI):

> request license fetch

• Verify the licenses again (or go to GUI: Panorama > Licenses):

> request license info