am failing to create the access token

Hello,

You need to ensure you are sending the “Ocp-Apim-Subscription-Key” header. Also please note that you need to be sure you are sending the right subscription key for the right product e.g collection or disbursement based on the API being called. 

Lastly verify that you are passing the “Authorization” header with details “Authorization: Basic ResultOfBase64Encode(ApiUser:ApiKey)”

Is ApiUser = username:password ?

ApiUser=username,  ApiKey=Password, but this does not mean the email or password you use to login into the portal. These are credential values generated using the User Provisioning API on sandbox and from the Mobile Money Partner Portal on production.