Ssrs 2012 is inconsistently displaying data

When I execute an ssrs 2012 report in visual studio on my workstation and on a test report server, the parameter value is loaded correctly for the report. When I run the stored procedure in sql server management studio pointing to the prod databases that loads the values to the parameters in the ssrs reports, the sql runs fine.

When I run the ssrs 2012 report on the production report server pointing to the production database, the parameter dropdownlist is sometimes populated and other times it is not populated. When I run the ssrs 2012 report with the same parameters, I can tell consistently when the parameter dropdown list will have values and when it will not have values.

Thus can you tell me what I need to look at on the production report server, to see why the
parameter value is populated in some cases and not in other cases?