Hi Sreenath,
Sorry for the delay in response. I hope you already have resolved this issue by now, if not, you may check this.
The patch you are trying to install is 17.011.30079 is an optional patch, often called out of cycle patch. DC Release Notes — Release Notes for Acrobat DC Products In order to install this particular patch 17.011.30079 you must have the very recent patch already installed on the machine which was 17.011.30078, if the patch is not installed it won't let you install.
Alternatively, you can install the next quarterly update patch 17.011.30080 which includes all the fixes or security fixes in it.
If you have further questions feel free to update the discussion.
-Tariq Dar