There are two problems that you may be facing:
First, if the screw won't budge at all, it's probably due to a little problem MT's been having with consistent application of thread locking adhesive. Your Tachyon probably has to much adhesive. Be very careful as the screw that secures the latch is a very small screw and, with the Torx head, you can, if there's to much thread locking adhesive, easily apply enough torque to break the head off of the screw. Then you'll be "screwed". There are three possible solutions.
A) There is a chemical solvent that can be used. But, Tachyon's construction will make getting the solvent down into the threads of the screw difficult.
B) You can heat the screw up (a soldering iron is often used).
C) You can send it back to MT.
Second possibility, the whole pin assembly is turning when you turn the screw head. The solution to this is to press down on the latch firmly so that the latch compresses against the pin and keeps it from turning so that only the screw turns.