PRO-92 serial communication
I have several different PRO-9x scanners including the PRO-92. All of the models I have use the same cables. While there are two main different versions of cables (COM or USB), I've also found different COM versions that all "work". There are several homebrew cables out there, the RS version and others. The reason I put work in quotes is because they all do not work exactly the same.
I have one COM version cable that, when plugged into the scanner, causes the message "press up..." to display. But when I open WIN92 and click on "upload to scanner" or "download from scanner", it transfers as expected and the message on the scanner changes during transfers. Pressing UP on the scanner, even when that it what it is requesting, does not work for me, as the software is not receiving. That prompt on the scanner is how you initiate a scanner to scanner transfer.
To answer a question posted; to initiate a transfer, press UP on the scanner which will SEND data. In other words, pressing DOWN (or other key) won't cause the scanner to receive; it is already ready to receive. The transfer must be started from the sending scanner.
Back to the original question; I have other cables which, when plugged in, do not cause the scanner to display the prompt message. All that is needed is to click the desired option in WIN92. So I believe your issue is tied to the SPECIFIC cable you have.
Another consideration is whether the plug on the end is MONO or STEREO. I've got an adapter that came with one of my cables. I've never had to use the adapter, but it could affect whether or not the prompt message is displayed. Just my $0.02.
Good luck.