The Problem
I've been trying to use Laravel Passport and I'm countinously getting the error {"error":"invalid_client","message":"Client authentication failed"}. I have used it in this Android and Laravel project but I just can register the user correctly as I see the proper data in the database. Then when the Android app tries to get the access token it crashes because the server return the previous error message.
I have also been following this YouTube tutorial exactly as it is explained but I got this error at the part it sends the "access token request".
Postman data
oauth_clients table
What I have tried
I have tried to fix this using this Stack Overflow page, this GitHub and many other webpages page but nothing worked
Possible cause
I think that it might be the uncompatibility of my laravel version and passport (see below). I have manually changed laravel version to 5.4 but I got a composer error. I don't want to reinstall laravel because i think I could crash all my laravel projects.
The 'user_id' column has to be populated by laravel (I have manually changed it to the user_id of the user and after that I restored it to zero)
How to print data to the console? I use error_log() but I can't print variable names and with dd()I get and error saying that the variable couldn't be converted to string.