I'm having the same problem.
Sangoma PBXAct, installed 2 weeks ago by Sangoma, all latest updates to everything as of last week.
Same symptoms. Users were copied over from the previous PBX, but passwords didn't work -- logins all failed. No Secret showing on Panel Manager -> Users -> any extension. Typed the Secret, selected the Template & Preferences, clicked [Submit Changes], user logs in. After they reload the page or log off/on to their PCs, the identically correct password stored in the browser fails. Clicking [Submit Changes] with no other input, they log in again.
???