Fatal Error using Client Credentials Grant type

Drupal Core: v8.7.9

I was able to use the Password grant type with no issues, but when I tried using the Client Credentials grant type I get the following exception:

The website encountered an unexpected error. Please try again later.</br></br><em class="placeholder">League\OAuth2\Server\Exception\OAuthServerException</em>: Client authentication failed in <em class="placeholder">League\OAuth2\Server\Exception\OAuthServerException::invalidClient()</em> (line <em class="placeholder">138</em> of <em class="placeholder">C:\...\vendor\league\oauth2-server\src\Exception\OAuthServerException.php</em>).

I am able to generate an access_token by POSTing to /oauth/token, but then when I try to actually use the access token I get the above exception. The exception also shows up when trying to debug using /oauth/debug?_format=json.

I have been issuing all of these requests to my localhost with postman.