When a client-user tries to connect to a Citrix-published application, sometimes they receive the error message “Can Not Connect To The Application. Citrix Protocol Driver Error.”
There are many reasons why you might get this error. In this article, I explain how you can investigate and eventually fix the problem by running through a series of steps.
The most common reason for receiving this error is that the server has gone down.
Check all the servers in the published app. Can you ping all the servers? If yes, can you RDP to all the servers? If there is a firewall between the client and the server, check the firewall logs to see if any connections are being blocked.
If there is a software firewall running on the client or on the server, disable the software firewall to see if this resolves the issue.
See if you telnet from the client to each server on port 1494. If not, reboot the server. If that doesn’t work, recreate the listener on the server.
The next step is to check in the eventvwr (event log viewer) on all the servers in the published app. Can you see any logs saying there is an issue with the Citrix license server, such as event ids 1004 or 1003? If yes, refer to Citrix article CTX564283 to troubleshoot these errors.
If “session reliability” (Common Gateway Protocol or CGP) is running, disable it and attempt to connect again. If you can connect after disabling the session reliability, find out what firewall port session reliability is using from the Citrix console and make sure that firewall port is open between the client and the server. Again you can telnet to that port from the client to the server.
If you are connecting via http (Web interface or http protocol within an.ica file) try disabling any internet proxy server you might have configured in your Internet Explorer settings. Also, make sure the “Automatically detect settings” is not selected, from IE > Tools > Internet Options > Connections Tab > LAN settings > Automatically detect settings.
The problem might be a Windows user profile issue.
Log on to the client machine with a different user id and try to connect to the Citrix published app. If you can connect, the issue must be Windows profile related. If you cannot connect there is most likely an issue with the client machine.
Update the Citrix client version. Go to the Citrix downloads section and download and install the latest Citrix receiver for your machine. If you are using an.ica file, open the file with notepad and look for the line that says ProxyType=Auto and change this to ProxyType=None.
Next you can try to reboot all servers in the Citrix published application.
It would also be a good idea to run Microsoft windows updates to install the latest service pack and hotfixes for your Microsoft operating system. Also make sure you download and install the latest Citrix hotfixes. (What’s a hotfix? Otherwise known as a Quick Fix Engineering (QFE) update, it is a single, cumulative package containing a series of files, used to address a specific problem in a software product – those pesky software bugs.)
Finally, if nothing else has worked in your attempt to solve your Citrix protocol driver error, install the latest Microsoft service packs and hotfixes on the client. If that fails you can try to reinstall Windows and try to connect to the published application from a freshly installed operating system.