After the uninstall of Server Virtual Delivery Agent 7.14, and install of Server Virtual Delivery Agent 7.5.1000, applications fail to load in seamless mode, and sessions remain open on the server even after exiting the application. 

An investigation with Process Explorer shows that twi3.dll has not been loaded into Winlogon.exe for this session.

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Customer moved the C:\Program Files (x86)\Citrix\System32 directory to the first place in PATH, and seamless is now loaded properly. Sessions also close gracefully.

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Problem Cause

The DLL responsible for starting the load of seamless functionality (ctxnotif.dll) was not loading correctly because a dependent DLL couldn't be find in the Windows PATH variable. C:\Program Files (x86)\Citrix\System32 was included in PATH, but a third party application's directory was taking priority.