You can double check the client id and secret are correct and don't have any trailing white space when entered in the FusionAuth config.
The scope you have configured does not show up in the discovery document but I would assume you'd receive a different error I'd that was a problem.
Confirm you registered the correct redirect_uri (something like http://localhost:9011/oauth2/callback) in your Intuit account.
Their APIs don't seem to be working well with the client_secret_basic authentication method.
Their discovery document indicates they support both client_secret_post and client_secret_basic.
"token_endpoint_auth_methods_supported":[
"client_secret_post",
"client_secret_basic"
]
The default OpenID Connect config in FusionAuth will use client_secret_basic.
I found a thread indicating others are also having problems with the Basic Authorization strategy.
https://help.developer.intuit.com/s/question/0D50f000050TBnCCAW/getting-the-errorinvalidclient-for-access-tokens
Switching the configuration to use client_secret_post seems to have allowed an authentication request.