@elpatron33 said:
ERROR 503
I can't use the Api I get the error: Response 503 Service not available.
Does anyone know how to fix it?

I believe this warning is not from TMDb Servers.
See the list of TMDb server error warnings here.
https://www.themoviedb.org/documentation/api/status-codes
In your case:

Code    HTTP    Message  
9       503     Service offline: This service is temporarily offline, try again later.  
46      503     The API is undergoing maintenance. Try again later.  

Post here the API Request that received this error warning.

Problems with API Request

In order for someone to help you with API Request questions,
it is critical that you post here the API Request you are sending to the TMDb server.
Remember to replace your Key with MY_KEY , YOUR_KEY , THE_KEY , or something like that.

Not the programming code/script you used to build the API Request.
But the API Request that is sent to the TMDb server.
Or the API Request you would like to send.

I'm having the same problem here in the 'Try it out' requests.

Yes, the "try it out" feature has been broken for a long time:
https://www.themoviedb.org/talk/600184fc6aa8e0004077e364?page=1#6001bbacbe4b36003d514ac3

But you can copy the web address and make the request manually and it should work.

Thanks fo Leon. I tried to copy the URL of my request and get another page with JSON file.

You're welcome. It sounds like you have managed to get the data you need. Please say if you need any further help.