This issue is caused when a large amount of data is being returned by the database query and the web service times out. Increase the execution timeout value in the web.config file and reset the IIS service to resolve this issue. 
  1. Edit the XML web.config file on the web server
  2. Locate the <system.web> section and change the timeout value to 31000 (use 60000 if this value does not work). For example: 
    • OLD: <httpRuntime executionTimeout="3600" maxRequestLength="32768" />
    • NEW: <httpRuntime executionTimeout="31000" maxRequestLength="32768" />
  3. Reset IIS (this allows the web server to re-load the updated config file)