No one here to open doors

Hi, I have a shift scheduled at 4 am, but so far no one is here. It’s only been about 10 minutes but I was wondering if anyone knew what to do in these situations. I’ve had a lead tell me before to wait 20 minutes and if no one shows then just leave. But I’ve also heard different things. Anyone know the actual rules that apply when an opener doesn’t show up?

Update: I was looking at my time and they switched my times without letting me know, and I just looked yesterday.