error=invalid_client_id for authentication

Question

I have enabled the Contacts app in SF to be connected and have the consumer and secret keys. Following the steps in

• https://developer.salesforce.com/docs/atlas.en-us.api_rest.meta/api_rest/intro_understanding_oauth_endpoints.htm

• https://developer.salesforce.com/docs/atlas.en-us.api_rest.meta/api_rest/intro_understanding_web_server_oauth_flow.htm

• https://developer.salesforce.com/docs/atlas.en-us.api_rest.meta/api_rest/quickstart_oauth.htm

• https://help.salesforce.com/articleView?err=1&id=connected_app_edit.htm&type=5

• https://help.salesforce.com/articleView?id=remoteaccess_oauth_web_server_flow.htm&type=5

and others on stack exchange like:

• https://stackoverflow.com/questions/12794302/salesforce-authentication-failing/29112224#29112224

My use case is customer used SOAP in Drupal 7 to push form info into Contacts. No other customer logins, just the API user for this form. I'm using the OAuth Web Server OAuth Authentication Flow since the keys will be transmitted by the Drupal form itself. Using these pages and copied my Consumer Key my curl is:

curl --verbose https://login.salesforce.com/services/oauth2/authorize?response_type=code&client_id=3MVG9oNqAtcJCF.GRBswvYTYwd7MV40M02g..8BCLONGSTRINGREDACTED&redirect_uri=https%3A%2F%2Fnew.mydevsite.org%2Fsalesforce%2Foauth_callback

And my return is:

Connection #0 to host login.salesforce.com left intact
error=invalid_client_id&error_description=client%20identifier%20invalid

My selected OAuth scopes are:

• Access and manage your data (api),
• Provide access to your data via the Web (web),
• Full access (full),
• Perform requests on your behalf at any time (refresh_token, offline_access)

Require Secret for Web Server Flow is TRUE and as I understand it that comes in when I get the initial code from this step in order to get my token for when the real work begins. I can't even get to first base with the authentication as I read in the help pages.

Am I even on the right track to use OAuth and REST? We're transitioning to Drupal 8 and the Salesforce module SOAP class is empty. I'm fine with REST, just am missing something.