This is useless as client_credentials can’t have scopes on them (so you won’t get the email address in the response anyway), as it doesn’t represent a user
This suggests something is causing ?login=fredthewaffl to not be sent with your request using this tool.
So the error of
{
"error": "Bad Request",
"status": 400,
"message": "Must provide an ID, Login or OAuth Token."
}
means, it got the token, but no ID or login. And couldn’t lookup the user that belongs to the token as the token is of type “App Access”
reqbin is probably messing with your request and it’s not calling what you think it’s calling.
As everything you are doing looks correct, so reqbin must be at fault.