Users upgrade the environment from XenApp 6.5 to XenApp 7.15 CU2. After the upgrade, when end users launch any applications and they maximize the window, the task bar in the end point device is covered by the maximized seamless app. In Xenapp 6.5 the seamless flag was configured to hexadecimal 0x48000, but in the XenApp 7.15 CU2 with the same flag applied, the issue still occurs

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Applied seamless flag 0xe8000, which includes:

1. Do not send disable (0x8000)

2. Do not send off screen Windows (0x20000)

3. Disable Language bar agent (0x40000)

4. Disable Client info Sync Except Workarea (0x80000)

Details
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Registry Key: HKEY_LOCAL_MACHINE/System/CurrentControlSet/Control/Citrix/wfshell/TWI
Value Name: SeamlessFlags
Value Type: REG_DWORD
Value: 0xe8000

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Problem Cause

In the users environment, the Seamless Flag (SF) 0x48000 was set on XenApp 6.5 IMA farm. When upgrade was performed to 7.15 CU2 FMA, that same Seamless Flag would not suffice. in IMA the seamless flag 0x48000 worked with the only graphics mode available but in FMA in which default Graphics mode is H.264, two additional flags had to be enabled for the use case in which all 80 SVDA's are 2008 R2 and the default graphics used is H.264. Therefore enabling the 0x80000 value (Disable Client info Sync Except Workarea and "Do not send off screen Windows" (0x20000) in addition to 0x48000 fixed the issue

Users upgrade the environment from XenApp 6.5 to XenApp 7.15 CU2. After the upgrade, when end users launch any applications and they maximize the window, the task bar in the end point device is covered by the maximized seamless app. In Xenapp 6.5 the seamless flag was configured to hexadecimal 0x48000, but in the XenApp 7.15 CU2 with the same flag applied, the issue still occurs

Seamless Configuration Settings - https://support.citrix.com/article/CTX101644
FarmTWIHelper - Seamless Configuration Helper Tool - https://support.citrix.com/article/CTX115146