HDX flash redirection might fail for certain flash content on later versions of internet explorer. This could manifest in a few ways.

1. Flash content appears to initialize but then hangs.
2. Pseudocontainer2.exe proces is created on the client side but the flash content does not play.
3. The same flash content may render fine on the server side if specified to do so using the URL compatibility list.

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• Enable Emulation Mode on the user device. In Internet Explorer, on the Tools menu, click F12 Developer Tools. In the far left of the DOM Explorer screen, scroll down the list and select the Emulation icon. In Document Mode, select 9 or 10. Microsoft Enterprise Mode Site List Manager can be utilized to automate the Document Mode.

1. Download the Enterprise Mode Site List Manager from here - Enable Internet Explorer Enterprise mode via GPO - https://www.microsoft.com/en-us/download/details.aspx?id=49974

2. Run the tool and enter the URL for the website you want to load in enterprise mode. Select the Compatibility mode you wish to use, I have chosen IE8 Enterprise mode. Click Save.



3. Click File > Save as XML. Save the xml file to a location accessible by the servers where the Internet Explorer instance will access the flash content (server VDA’s). 

4. Open group policy and go to the following setting - Administrative Templates\Windows Components\Internet Explorer\Use the Enterprise Mode IE website list

5. Enable the setting and point it to your xml file from the previous step.

6. Now after launching IE and browsing to the website you will see that it is running in Enterprise mode and flash redirection is working as expected. I have included some reference documentation below for your review.
 

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Problem Cause

Adobe Flash technology and content is frequently updated on many websites that might impact Flash Redirection particularly with Internet Explorer 11.

https://support.citrix.com/article/CTX136588

https://docs.microsoft.com/en-us/internet-explorer/ie11-deploy-guide/turn-on-enterprise-mode-and-use-a-site-list

https://docs.microsoft.com/en-us/internet-explorer/ie11-deploy-guide/fix-compat-issues-with-doc-modes-and-enterprise-mode-site-list

https://docs.microsoft.com/en-us/internet-explorer/ie11-deploy-guide/use-the-enterprise-mode-site-list-manager