I don't have the app, so I provided the address to Postman https://www.postman.com/
I followed the instructions https://developer.themoviedb.org/reference/authentication-how-do-i-generate-a-session-id
I work through postman

https://api.themoviedb.org/3/account/###/favorite?api_key=###&session_id="####"  

{ 
    "media_type" : "movie", 
    "media_id" : 1184918, 
    "favorite": true 
}  

error Authentication failed: You do not have permissions to access the service