Could you be a bit more specific as to your setup regarding phone lines. Did you get the Fax browser opening to show you the fax being sent and a confirmation? Did you hear a dialtone? etc...
What kind of doc did you try to send? Not everything is faxable.
Anyway, it's been a long time since I used Faxstf (or OS 9 for that matter) but I remember having to juggle settings in a few places to get it to work. There's something about getting the port setting to choose your modem as a printer, I think. Like the old chooser? Boy, I've forgotten so much since going to X.
Just dug in my OS 9 partition and found the Faxstf manual. If you don't have it I could send it to you. It's just under 1 MB in size. I would need a current email address which you can send to me in a PM.
I was hoping for a simple fix. I don't enjoy reading manuals but I appreciate your offer anyway.