Boy do I need some help!
As per @bkahl 's information about the release of Marlin 2.0.9.0.6, I attempted to flash it to our Workhorse via serial connection in CuraLE 3.6.25. The update failed, and now there is only a blank screen on the printer, and it won’t connect serially.
How do I recover?
Have you tried to use the automatic upgrade firmware to see if the printer is able to receive firmware? If the upload fails, you should be able to reupload firmware without any issue.
If the issue persists, I would recommend trying another USB port/cable combination.
Ah, sometimes the simplest solution is the least recognizable. I was one scared puppy for a bit. 
The printer was not showing a connection in Cura, but the automatic upgrade flashed just fine anyway. That was after I dragged out the laptop and connected directly with a short cable. 
Thank you for the quick response, @bkahl!
No problem at all! Happy printing!