Grey Screen On launch of  Windows Server VDAs which were Upgraded from XenDesktop 7.6 LTSR  to XA/XD 7.15 LTSR or CVAD 1912 LTSR.

Windows desktop VDAs are not affected with this issue.

As a workaround, Delete this regkey on the VDA, HKLM\Software\wow6432node\Citrix\CitrixHook\AppInit_DLLs\HDXMediaStreamforFlash.

Fix for this issue will be released in LTSR 1912 CU1.

Problem Cause

CtxUvi.sys driver has encountered an error as the verification of HDXMediaStreamForFlash failed.