As a user assigned to Report Player opens up a report, the application finishes authenticating the user. When the user goes to the Run tab, it is left blank with no parameter selection or Run button.
This is caused by the user having the "Show the Start screen when this application starts" option checked in Excel Options General. The Report Player window actually opens up in a window behind the report. The Player window may not be visible in the window behind the report.
Uncheck that box and whenever a report is opened, the Report Player window should appear correctly.
Report Player Designer 4.6