Problem/Bug Can't build within a certain area on my own server

I came across a very wierd bug on minecraft. I was just building a tower in a PVP arena and minding my own bussiness when all of the sudden my blocks that I placed disappeared not even a millisecond after placing them. I first noticed that when I did '//up 0' to build in the air and the glassblock wouldn't go away. I have tried various diffrent solutions but I never came across one that worked such as changing the spawn-protection, giving yourself OP or looking for typos in the PermissionsEX. I can build where the spawnpoint is, my Permissions-folder is an exact copy of another server which I am a dev on (I borrowed the file since it's a local server and I tried using his permissions-folder to see if that worked) but nothing seems to be working