Could not connect to debugger

When i type a script in MonoDevelop, and something is wrong with it, i have no idea what, because when i try to debug, an “Attach to Process” window shows up, and it never has before, so i have no idea what to press, Unity, null(mono), or USB iOs. When i press Unity or null(mono), it waits a second then says “Could not connect to debugger.” I’m using mac if that helps. Thanks!

did you ever find a solution? I am on windows and having the same problem.