There are multiple solutions to go for in this case:
The frontend.dll file might be corrupted. You can resolve this problem by moving this file from another PC with a working install to the corresponding position: C:\Program Files (x86)\National Instruments\TestStand 20XX\Components\Callbacks\FrontEnd\Win32\frontend.dll of this PC.
If the above solution didn't work, try repairing or reinstalling the NI TestStand Software
Collaborate with other users in our discussion forums
A valid service agreement may be required, and support options vary by country.