500 internal error using PaaS, working fine on local

[fullfine]

Hi!

I am developing a tool that takes songs of Youtube and creates a playlists in Spotify. I have run the application succesfully in local, but I get an error when I try it in Elastic Beanstalk, the PaaS of Amazon. 

I am using a Flask server and the Spotipy python library. I think that the problem is related with the redirect_uri, but I have no idea of what I should do. I create two spotipy objects in my code. The first one, using Client Credentials Flow, works perfectly online. However, when I try to use another one with Authorization Code Flow, I get the error. I can even create it, but when I call to any function, even to search tracks, I get the 500 internal server error. I assume that the redirect_uri has to be the same url where the app is launched. 

Thanks in advance!