When i try to view some logs like admin or audit, i see the results, but when i try to export them, all i get is a blank excel sheet. This works fine with computer status logs. Is this a known issue?

Whats the exact version?

Is it from remote web console or from SEPM? Seems to be a know issue if you are running older version of 12.1 , here are the two articles which explains 

Cannot export Symantec Endpoint Protection Manager 12.1 Release Update 2 logs or reports.

http://www.symantec.com/business/support/index?page=content&id=TECH200948

Symantec Endpoint Protection 12.1: Unable to export logs from Manager using web or Java console

http://www.symantec.com/business/support/index?page=content&id=TECH200948