Error connecting to Mattermost 5.37.3 on Windows XP

After upgrading from 4.4.5 (via 5.33) to 5.37.3, Mattermost hangs when loading. Only the loading screen with the 3 dots is displayed.

Steps to reproduce
Mattermost Server 5.37.3
Firefox 52.4.0 on Windows XP
Calling the normal URL of the Mattermost Server → Stuck

Newer PCs (and the Android app) have no problems.

I know that Windows XP is very old. But that’s why we use Mattermost for internal communication. The PCs do not connect to the Internet.

Windows XP has not been supported since 2014.

You would have to go back to your previous version if you want to continue using windows xp.