@Serth - Sounds a bit like one of the complexities DMR-X users had, where the often quoted methods were based on earlier CPS versions on gear with earlier FW, whereas a lot of the problem rigs had later FW (the radios marked DM-X vs DM1702B) and needed a different CPS revision.
Add what Paul mentions too, and really there’s no end to quirky reasons for comms failures or non-detection of devices.
But all things being equal and having the right match of revisions, it’s a case of run & go or ■■■■ - back in the day, when we used RS232 (real RS232 ports) and Unix/Linux/DOS and DOS/Win3x, it was actually less of a minefield. Especially with non-Win, it was just a matter of software accessing the connected device in a DTE-DTE or DCE-DTE. Connected manner and effectively the whole program you transferred got sent as a batch of plain ASCII plain text or using a binary transfer similar to how we used to upload/download via modems using XModem/YModem/ZModem protocols.
There were no obscure ‘virtual device’ and subsequent translations virtualization requires. It either worked or not, and failure was either through time-outs, power glitches, duff cables (intermittent connections) or wrong comms settings - aside from intermittents, which are always ■■■■, every other combo were easy to diagnose.
Needless to say, I never discarded old serial cards as there’s still a lot of gear that don’t play ball with USB-Serial adaptors.
But irrespective of how the transfer and interchange works, the equipment needs to be in the right mode else even if it appears on Device Manager as a com port or USB device such as a bidirectional printer, in the wrong mode (not in exchange/cloning/programming mode) the software won’t be able to communicate with device.
With real serial or JTAG ports on device, the port was usually live as long as the device was powered, hence why JTAG/TTL serial is the most commonly used device hacking direct route to sniffing and reverse engineering traffic.
Most of those router hacks you see, such as open source f/w replacements would probably never got built without some kind of reverse engineering based on low level access and traffic sniffing.
Good luck, i hope this doesn’t turn into a new DM-X equiv ongoing problem.