The CommServe and the web server is the same machine. But the problem is solved now. It turned out that CommVault could not communicate with ActiveDirectory. I checked the D:\Program Files\Commvault\ContentStore\Log Files\WebServer.log and the AD service account specified in the CommVault AD setup could not communicate with the domain controller. Checking with our domain admin, it turned out that the service account was locked out. So unlocking the AD service account solved the problem.