OAuth 2.0 Client Credentials Grant Failing with 500 Error

After our upgrade to Version 12, we are receiving a 500 Error when trying to use OAuth 2.0 Client Credentials Grant:

Request:

https://sugarclub.sugarcrm.com/api.ashx/v2/oauth/token

Screenshot in PostMan

Response:

{
"error": "server_error",
"error_description": "The authorization server encountered an unexpected condition that prevented it from fulfilling the request."
}
This was working before the upgrade, and Im not sure how to find what the underlying issue is in the Administration section of the community. Any assistance is appreciated.