sql server Report Server Configuring

One of the things that always seems to work for me in a case like this is checking the "Log On As" data which is found in "Computer Management" console under "Services". Assuming we're talking Windows here, scroll down to where the SSRS instance of the SQL Server alias is in the list (something like "SQL Server Reporting Services (X...)" and right-clicking "Properties" contextually, bring up the "Log On" tab and fiddle with any of the various settings combinations in that panel. There are only a half dozen or so combinations that make sense. One of them might remedy the situation. If you're paranoid about changing a setting, write all the parameters down first before you try a new set of them.