Endless loading screen in LMS in Mozilla Firefox browser

Symptoms 

On attempt to access the LMS via Mozilla Firefox the following white screen appears: 

Cause 

By default third-party cookies are not allowed in Firefox: by default it is cross-site tracking cookies and it isolates other cross-site cookies option. 

Resolution

    1. In Firefox open Settings > Privacy & Security, check that Enhanced Tracking Protection is in 'Standard' mode:

    2. Scroll down to 'Cookies and Site Data', click Manage Exceptions.

    3. Type in address 'https://idp.constructor.app' and click Allow:

    4. Click Save changes:

    5. Open LMS website and log in.