osTicket shows 'Authentication Required' error after upgrade from an old version. Clearing cookies fixes it temporarily but sessions expire quickly.

Truncate the ost_session table in the database and clear all browser cookies/cache/sessions (or use an incognito window). Disable 'Bind Agent Session to IP' in Admin Panel > Settings > Agents. If on a load balanced or proxy/Cloudflare setup, ensure TRUSTED_PROXIES is configured in ost-config.php. On v1.18.2, this was a known regression -- upgrade to v1.18.3. If v1.18.3 makes it worse for your setup specifically, re-apply the session commit that was reverted: https://github.com/osTicket/osTicket/commit/c3819e4d21b8fcd4073713a9485a9057b82b89fc