PDF Files Can't Find Printer

I'm using the latest version of Acrobat Pro DC on a MacBook Pro running El Capitan v10.11.5, trying to print to an HP OfficeJet Pro 8500 A909n, and no matter what I do, no pdf will print.  I keep getting a message that the file looking for the printer, and it remains hung.

The printer *is* online, the driver is current, and it prints just fine from everywhere else I've tried, just not from Acrobat.

The files came from DropBox, and even after saving them directly to my hard drive, the problem persists.

I've tried everything I can think of and can find online for troubleshooting, including checking the syntax in Preflight, and everything checks out fine.

Please help; I'm desperate!

Wendy