Noticed that for a client, all their PCs were unable to print labels from UPS.com after upgrading to Windows 11.
It kept saying no thermal label printers found.

After a lot of troubleshooting I found the answer.

I dug into the UPS Thermal Printing App, located here, and found that the tool REQUIRES that the vendor name needs to be in the Name field for the printer.

It appears during the Windows 11 upgrade, it renamed the printer to match the driver, in this case “ZDesigner Gk420d”.
Once I prepended it with “Zebra”, the app magically found it and printing started working again.