I used to have SD1 and without a seriel port in my lap I use an adaptor USB to Seriel ,like you have.
First you should check if the Ketron cable it's ok.Try to find someone with a classic seriel port and make some tests.
Then ,after you install ketronFT, try to change the seriel ports.Sometime it needs to test some other from the list.It should work.
If you need a schematics for Ketron PC cable, eventualy to check if the cable is ok by measuring with a ohm-meter , see the connection diagram at www.caia.tk
, under "Diverse"
Hope it helps,