You misunderstand, Jelly. Derpz and Three Million weren't talking about whether or not the .wav file was a looping one. They talked about a spawnflag that ambient_generic has named 'Is NOT looped'. This spawnflag changes how the playback of the ambient_generic is controlled. If you tick it, the entity will restart and play its sound whenever it's sent the PlaySound input. If it's not ticked, then the entity must first be stopped before it can be told to play again.
Your logic_timer OnTimer output has a delay of sixty seconds. Assuming your logic_timer has a sixty second refire interval (Class Info tab), your output is actually firing in 120 seconds (60 + 60). Set the refire interval to 60 and remove the delay on its output.

Unticking the 'Is NOT looped' flag will make the game assume the sound file is a looping wav. The game automatically stops any looping sounds when the round is reset, so this is useful for preventing overlapping music.