Thanks a lot for your reply Sayeed, so it means that which i assumed that configured regular expression was the reason for the issue (file systems have been removed from monitoring after unmount/mount activity).
So just need to make blank field of Ignore_File_System and this issue will get resolved.
One more thing which i want to ask that if i would make this change in package of Linux and deploy that on all Linux servers, would it enable the monitoring on all the file systems on server which had been removed earlier due to unmount/mount.
Regards,
Manish Sharma