"User not registered in the Developer Dashboard" error with additional users on app

[royal4206]

Plan

Premium

Country

Switzerland

Device

Windows; Desktop / PC

Operating System

Windows 11

My Question or Issue

When attempting an oAuth request with Spotify from either a Node JS (using passport and passport-spotify node modules) or C# (using "AspNet.Security.OAuth.Spotify") app, I am unable to get the other users I have added to my Spotify app (which I can confirm that their emails and names are all correct, even going as far as putting usernames as their names), however when they go for the authorization, the Spotify app allows them in, exchanges the tokens but does not let my code access anything beyond that with the error of: "User not registered in the Developer Dashboard".

It's important to note that the authorization and further API requests as myself (logging in under the same account as the one which the application was created under) works fine.

I have additionally gotten my friend to do the same type of code, on a different Spotify application to see if it was something on my end and it wasn't.

I have attached the error log from the C# application, which has the most detail to this post, as well as a screenshot from the NodeJS error as well.

I am very confused and a little annoyed that this is an issue. I also apologize if any part of this does not make sense, I am writing this very late after hours of debugging only to find it's not a problem with my code, and I'm happy to reclarify or go into detail further for parts that don't make sense.

[qorrect]

That solution worked for me actually, waiting on quota extension to be approved to test the second half of it

[Efremych]

I don’t know… additional user can “read”, but can not “write”. How the quota can fix this. 
In any case, I abandoned this idea (I has been tried to bypass another API error by adding an additional user).

[spotl1ght]

I am receiving the same 403 errors here is my code - what am i doing wrong 

sp = spotipy.Spotify(
    auth_manager=SpotifyOAuth(
        scope="playlist-modify-private",
        redirect_uri="https://example.com/callback",
        client_id="180589cc8b96411884d0a79458009cd1",
        client_secret="xxx",
        show_dialog=True,
        cache_path="token.txt"
    )
)