Invalid_redirect_uri on OAuth 2.0

I am trying to add an OAuth 2.0 to my website, following this documentation

So I did All steps

here is the error
{‘error’: ‘invalid_grant’, ‘error_description’: ‘invalid_redirect_uri’}

I checked several times and I am 100% sure that the URL configured in the application is the same in the authorisation step,
The URL is on HTTPS.
I tried to create several applications on several accounts and I get always the same error

So do you have an idea why I get this error?

I found the sollution

According to the documentation

1- The redirect_uri is optional : but it’s mandatory
2- The parameter is redirect_URI, but this doesn’t work; the parameter that work is redirect_uri in small case