Pull the hood trigger to open the hood but the hood is not opening

This is one of two things most likely. First the latch is frozen and not releasing. If this is the case then you may be able to have someone pull the release handle and hold it then shake the hood where the latch is and see if it will work loose.

Second, the cable is frozen so even though you hear the latch working it may not be pulling the latch open. If this is the case then you may have to see if you can remove the handle and pull the cable with a pair of pliers.