1.5mm Hex Key

Hey guys,

I am having an issue with unscrewing with a 1.5mm hex key. whenever I put the hex key into the screw, it only rotates without unscrewing as of there is no locking mechanism at all. I have 3 screws that need to be untightened. I was able to do the first one but not the other two. I am pretty positive it is the correct size but somehow there is not enough friction. I have tried hot glue, a toothpaste and Valve Grinding Compound to put on the hex key to induce some friction but all failed. Any ideas?

Thank you in advance!