"The connection either timed out or was lost. Unable to read data from the transport connection: An existing connection was forcibly closed by the remote host."
There are two possible causes.
1. If you are getting this error randomly while opening the report.
It is likely that your Analyzer site's authentication setting is not setup correctly, most likely both Windows and Basic authentication both are enabled. You should only have one or the other enabled - ASP.NET + Basic or ASP.NET + Windows, never both Windows and Basic together.
2. If you are getting this error while using Chrome browser only:
Please try to reset the browser or find a freshly installed Chrome browser that is free of extension or plug-ins to see if it works.