On my iMac running High Sierra, IntelliType 8.2 suddenly stopped recognizing my MSFT Ergonomic 4000 keyboard. One day it was working fine, not the next. After attempting everything, including reinstalling the OS, I finally called Apple Support (MSFT Support had been useless).
I was fortunate to get a great guy, Andrew B in North Carolina. He figured out what we had to do. The culprit was Apple's "System Integrity" patch, which they added to their OS starting with El Capitan. The solution was to turn it off. Here's how:
1- Launch Terminal and enter: csrutil disable Then hit Enter.
3- Reinstall your keyboard/mouse driver (must do this!)
4- Restart, and all should be AOK!
Andrew recommends turning System Integrity back on following Steps 1 & 2, using "... enable" in Terminal. I elected to leave it off to avoid similar future issues.