Mobile Printing & Cloud Printing

I have two HP printers wired directly to my network.  They both work properly on Windows PCs over both wired and wireless connectons.  They had both also been working properly on various Android phones and tablets connected wirelessly to the same network subnet that the printers are on.  The newer printer, an HP Color Laserjet Pro M452nw (wifi direct disabled), was -- and still is -- working via the default Android printer service.  The older printer, an HP Laserjet P2015dn, has never worked with the default Android print service (the service cannot find it at all); but the HP Printer Service Plugin for Android used to work without any problem.

Recently, I have found that the HP Print Service plugin no longer detects the P2015dn.  When setting up new Android devices, the service will not install the printer; and the devices on which it used to work, it is now always listed as unavailable.

I have tried installing several other Android print services, but none of them recognize the P2015dn either.

Both printers are on the same subnet.  Both printers are configured for DHCP, but use specific IP address reservations (essentially giving them static IP addresses, but allowing me more control).

The M452nw is automatically detected by the default Android Print Service.

The P2015 has always been unavailable via the default service, but available via the HP service (added by entering its IP address), but now is not.

When I try to install the P2015dn by IP address, it cannot be found.  The HP service says, "Unable to communicate with this printer."  When I try to print to it on devices that i used to work on, I see, "The printer is unavailable."

The problem has only started recently, and may be related to the devices being upgraded to Android 9 (I'm not sure exactly when it started because we don't print from them frequently).

According to documentation on the HP Support website, the P2015 is still compatible with Android devices via the HP Print Service.

All drivers are current.  I looked for, but could not find any HP printer drivers for Android; and the Linux drivers do not work with any of our devices.

I have tried the following:

Power-cycling printer, router, and all Android devices.

Stopping all print services on the androids, and deleting all application data for them.

Uninstalling all third-party print services, and then reinstalling and trying them again (one at a time).

Resetting network connections on each Android device.

Enabling all network services on the printer.

Any suggestions would be appreciated.

Thanks,

Phil