Server Error in '/' Application. Method not found: 'System.String Elearningforce.SharePoint.DB.ListInfo.get_FieldsSchema()'.
The reason of the error is a mismatch between lms and common solution versions. The issue occurs when you're using SPLMS ver. 3.2 which is dependant on a lower common ver. <=18.104.22.168, but you're running a higher version of the common solution.
To fix the problem it’s necessary to upgrade to lms version which supports a higher version of the common dependency solution, that is SPLMS 3.3 which you acn find on the downloads portal.