Coroutine yield return new Waitforseconds not working

You are calling it correctly. By chance have you tried lowering the wait to 1? Sometimes 5 seconds can seem like and eternity when you're testing.

Yeah, I've tried 1 second. Still doesn't work. Any ideas?

There are several things that could cause a coroutine to stop. The most common thing that I have seen is the object being destroyed during a coroutine through some other event. Subsequently, the coroutine will be destroyed with the object that was running the coroutine.

Disabling the game object the script is attached to or setting Time.timeScale = 0 will also stop coroutines.

@Zhinkk, feel free to post the solution you found as an answer and mark it as accepted. It is perfectly fine to post and answer to your own question when you discover what the problem was. That way other people with this problem can see what you did to solve it when they run a search.