We are running SQL Server 2008 R2. All these reports were working fine until we upgraded IE from 10 to 11. Every time we run a report, it will just stuck at loading forever.
Tried changing the document mode to other versions.
Per the OP, add the site to Compatibility View.
It's also possible that the browser detection needs to be updated on the server side for .Net per this blog article. Basically, there's a hotfix for ASP.Net 4.0 and one for ASP.Net 3.5sp1 and ASP.net 2.0 that you need to apply. Alternatively, you can update to ASP.Net 4.5 which will also fix the 4.0 issue.
You might need to upgrade to your SQL server to Service Pack 2. There are several issues compatibility issues with ie10+ and SQL Server 2008R2 RTM.
ReportViewer's Print Button Incompatible with IE 10?
The following table lists the major releases of SQL Server 2008 R2. Release Product version SQL Server 2008 R2 Service Pack 2 10.50.4000.0 SQL Server 2008 R2 Service Pack 1 10.50.2500.0 SQL Server 2008 R2 RTM 10.50.1600.1
Microsoft Article on Server Version
Connect to the instance of SQL Server, and then run the following query: