Also watch that older versions of legacy program only allowed com1-4 to be selected where as later OS's could assign a device outside this range - i have com 9 and 18 assigned to various USB/serial devices. So you need the latest legacy program if your USB/serial adaptor assigns com port >4 or try and force com port to 1-4. Best to get newer legacy program if you don't have that.

Meridian owner since 1992
Prime & PSU, Focal Elear headphones, Roon (ROCK 8Gi5 NUC), Explorer 1 & 2, F80. 200/203, various Sonos (via Roon).