I'm using v18.104.22.16813 64-bit Professional.
I'm using the file from Ed's UNO2 that I created for Guitar Rig5.
In the Standalone version of BIAS FX, which I hadn't used in ages, I loaded it all up, configured the drivers and MIDI settings, and assigned CCs and Expression pedals without problems. I don't know how that "Generic" file is set up, but it could be that the author is only using a single Value (0 or 127). That would explain why it's needing two presses to get a change. Try my GR5 file.
As to Ableton, before I could get BIASFX to work properly in Ableton I had to get it set up and working in Standalone Mode. IDK why, but once I did that it worked properly. Attached is a screenshot of the configuration in Ableton.
EDIT: playing around with this some more, they haven't changed the MIDI toggle function, it still merely flips the ON/OFF status on receipt of EITHER 127 or zero.
I still hate Positive Grid. What this means to you is that even if the author of the generic control file only used one value, it should work.