Have some faith that the seat is yours, and maybe reach out to the professor. Maybe they'll let you audit the course or register late. People drop classes all the time,  and I'd  also advise continuing to check the course  if your school does online registration like mine does. They could update that listing as people add/drop the  course!

I'm a university lecturer. Most departments want to fill every place to maximise revenue. An empty seat is money not in the bank.

It's been a long time since I posted a reply. But I wanted to post an update since a miracle happened yesterday.

I was sitting at home watching a movie with a few of my friends fron college. They were talking about classes this fall and I had this weird feeling to check and see if the class I wanted to take was still open. Well I checked the registry and there was 1 seat open! The professor grant me his permission to take it and I was over joyed! That class being open allowed me change my schedule into a WHOLE lot better one and I get to be in classes with the people I enjoy.
Funny thing is, after I made these changes, I told my friends about it and they looked vert confused. They told me that they couldn't make changes to their classes because the registry is locked in the summer. I was quite dumbfounded. How was able to make class changes if the registry was locked? There was no way the instructor unlocked it for me because no staff has access to that, only advisors.

Putting two and two together, I finally figured it out.

Back in April, when I was worried and being negative about the class, I received no result because I didn't LET GO.

Now don't let me confuse you, I didn't give up. Deep down in my heart, I KNEW I would be able to take that class. But I didn't stress about it as much because I knew I had 2 months. I just let go of my negatively towards it and being obsessive.

Now, 1 month later, I forgot all about it and then suddenly I had the urge to check it. The Universe gave me the opportunity, and I took it. The Univers not only allow me a seat in this class but gave me access to change my schedule.

LOA works guys. You don't need me to tell you that. I have always beleived in LOA. There are times where I feel negative and just want to give up but I don't. I'm never giving up on the universe And you shouldn't either.