Despite the fact that in 5 years of coming to the pool boards I've never seen a question regarding 'getting sticky safety cover anchors up', I'll address it anyway. If you go to use the Allen Wrench and the anchor won't come up, pour some water on it and work it up and down, what's happened is that grit and debris has gotten into the threads and the water will help wash it out . Sometimes they are so stuck that you need to put an adjustable wrench on the allen wrench to get extra torque , don't try to force it too much or you'll strip the brass, slow and steady wins the race - apply water as needed until you can get it all the way out, then rinse both the socket and the anchor threads.