Videos won't play in Internet Explorer 10/11

Symptoms
Videos won't play in either IE10 or IE11.

Cause
Client side rendering is enabled and the launcher machine doesn't have Flash installed. (Must be the same version as the target environment).

or

This problem can occur because the Desktop Experience feature in Windows Server 2008R2 does not include decoders for the H.264 and AAC formats. 

Solution

1. In case of client side rendering please ensure that both the launcher machines and the target environment run the same (latest) version of Flash. It is also possible to disable Flash redirection. 

You can set flash redirection with the Citrix policies or you can add a regkey:

On the launcher machine: 
Key Name: HKEY_LOCAL_MACHINE\SOFTWARE\Policies\Citrix\HdxMediaStreamForFlash\Client\PseudoContainer 
Name: UseFlashRemoting 
Type: REG_SZ 
Data: Ask/Always/Never

On the  server machine:
Key Name: HKEY_LOCAL_MACHINE\SOFTWARE\Policies\Citrix\HdxMediaStreamForFlash\Server\PseudoServer 
Name: UseFlashRemoting 
Type: REG_SZ 
Data: Always/Never

2. Try enabling this setting in Internet Explorer, Tools > Internet options > Advanced > then, under "Accelerated graphics", mark the checkbox in front of "Use software rendering rather than GPU rendering > OK > then restart IE.

3. Install the Desktop Experience Decoder Update for Windows Server 2008R2. This update adds the H.264 and AAC decoders to enable playback of these formats.

http://www.microsoft.com/en-us/download/details.aspx?id=13283

Properties

Applies to
Login VSI - any version.

Resources
https://support.microsoft.com/en-us/kb/2483177