Hey Saranya,
First of all, I would recommend that you create a service request with support since VLM is not really supported by the forums. To do this, go to ni.com/ask.
Secondly, what we will need for further information is the debug log (located in C:\Program Files\National Instruments\Shared\License Manager\bin\lmgrd.log) as this will provide the most reliable account of check in/out operations.
Thanks,
Andy McRorie
NI R&D