Posting this in case it helps someone else. Client is on SPC (new), v2022.2, and we received this error when trying to add a UDS (clicking the green check-mark button to verify syntax).
The script host was properly installed (and Allow External Access enabled), with correct file association, but it turns out they were running the 64-bit version of Sage 100.
Changing to 32-bit (running the utility) fixed the error.