HP Designjet 500 hassles (& solution)

My HP Designjet 500 stopped talking to my old HP desktop (W10) about a year ago. Then in April 2020 I bought a new Lenovo desktop that also runs W10. Badly needing the 500 to print something I monkeyed with it for hours, testing the cables, trying new drivers, the useless Windows troubleshooter, etc. etc. with no luck at all; not even a test page would print. Kept getting messages about a "0x0000007f error." Somehow I stumbled on the "HP Print and Scan Doctor 5.0.7" on HP's Support site and downloaded and ran it (pretty user-friendly); I was immediately able to print a test page and then to my surprise was able to print from my drafting app just like the old days. Very pleased. Would not bet the farm that this is a permanent fix.Though it seems like one.