Thought I’d pass on how I eventually was able to make my IN-DB9 foot pedal work with Express Scribe through a serial to USB adapter.
I had a Bluetooth dongle installed which was using 7 or 8 COM ports, and specifically the COM4 port. I had to uninstall the dongle and the USB adapter in order for the USB adapter to be able to be installed on COM4. When that was done, Express Scribe was able to go through the COM4 port to get to the foot pedal.
Then I just reinstalled the Bluetooth dongle for my other needs and Bob’s your uncle.
The adapter is Aten USB to Serial Converter (RS-232).
Hope this helps others.