So I gave this a go.
Your messages up until you get the no serial port message are correct.
If you have no cable you get a different error message. Thus the computer found your usb to serial converter.
I see you were connected to serial using 9t11. All was well.
Try power cycling the pmc8. This seems to be indicating the serial port is broke. Maybe your db9 connection is no good. Unplug it and replug it. Something simple maybe.
Wes, Southport NC
EXos2-GT PMC-8, iExos 100
ES ED 127, 10" LX200GPS+wedge, Astro-Tech 8" Newt, ETX-90, 60mm no-name guide scope ~ 260mm FL
Polemaster, Orion ST-80 and SAG, ZWO 290MM, D5300 astro modified
Nina, Bootcamped Mac Mini control computer, RDP to iMAC
110 amp hour lead acid deep discharge battery for field power
Electrical Engineer, Retired