We're going to need a bit more information to help you with the troubleshooting.
1) Does Coresight work locally on the Web Server?
2) Is everything properly configured? Navigate to the admin page for Coresight and verify that communication with SQL is good, PI Data Archive, AF Server and PI Web API.
3) Any indicative errors in the following logs on the Coresight server, Application Logs and OSIsoft-PISymbols ?
It seems like this issue may be of high priority. If it is, I would recommend contacting our support engineers to speed up the troubleshooting process. We can then come back here and post the solution for the folks reading this thread.