The widely recommended RS232 to USB adaptor is the Keyspan USA-19HS. Others do work but if you’re having problems the Keyspan is a known quantity and takes a lot of unknowns out of the equation when you’re having a battle to get it working. I think they are still available.

Having said that the main thing that gets missed when you’re first trying to get this working is that you MUST have a null-modem cable (I think it swaps the Tx and Rx connections compared to the standard RS232 cable?).

Good luck, it’ll be worth it.

Richard