Windows 11 PCL XL UnsupportedProtocol Error with HP LaserJet 4050

[BWAZ]

Attempting to install HP LaserJet 4050 on Windows 11 computers.  Printer worked fine on Windows 10 machines.  Still works with Windows 7 machine.

Printer is connected via an LPT cable to a Silex 200 print server which is connected by Ethernet cable to my router.

Have tried multiple ways to install drivers and printer on new computers.  Test Print sends to printer but prints out PCL XL error, UnsupportedProtocol.

Windows 7 installation still works with LJ 4050.  Uses UNIDRV.DLL and hpmcpap6.gpd.  There is a UNIDRV.DLL in the drivers>x64>3 folder but hpmcpap6.gpd is not there.

HP Support will not recognize the serial number of the LJ 4050, USQA039561, so the various diagnostic tools cannot be accessed.

LJ 4050 printer is used to print out large page number files such as legal filings and documents.  I need it to work with Windows 11 machines.

[BWAZ]

Solved the problem after two days of working on it.

It is simple.  During the installation you will see a dialogue box asking which driver you want to install.  DON'T select either of the current installed PCL 6 drivers.

Instead, click on the Windows Update box.  It takes a long time for Windows Update to find all of the drivers.  However, eventually, you will see a listing of manufacturers and printer models.  Select HP and the model you want and the correct printer drivers will be installed and the printer will work just like it should.