When creating new payment services or when adding new users to Dynamics Online, we need to ensure that we are assigning proper roles to these services. This user role can then be used to enter in the Payment Services setup in AX in conjunction with the service they have access to. A newly created Microsoft Account or user within Dynamics Online will not have any roles assigned until they are manually added. Thus they will run into "service unavailable" errors when attempting to log into the service at https://www.dynamicsonline.com. We will need to modify this user to assign any services and roles they should have access to in the Customer Portal so that they can either make payments using that service or access the customer portal administration for that service. Below are the steps for adding user roles.
If you have any issues with the setup, access, or other errors in Dynamics Online, I would suggest opening a support ticket for an engineer to assist you.