Due to a bug with authentication plugins not displaying the “LOGIN WITH XXX” button the Devs over at osticket.com just pushed a hotfix version 1.15.3.1.
The patch notes for this read:
Improvements
- Auth: Service Name (da05573)
If you were already running 1.15.3 please upgrade immediately.
The new version is of course available over at https://osticket.com/download