We were facing a similar issue when integrating XSUAA with mendix, some of the things that you would have to check is if the role-template mapping is done in your SAP instance. You would have to add a role mapping where the Anonymous user should be mapped with Administrator role - since when you login with XSUAA creds the role of the user login will be anonymous and should be provided the Administrator role for the system to allow XSUAA to create a Account object for the login.
Also check the security configuration of the SAP instance that the SAP user account is provided the required access.
"They will be assigned to the roles in the Mendix application based on the scopes they have received from the XSUAA service. The scopes are defined by the mapping between the role templates and the role collections."
What are your User Management setting for your user (role)?
I see that your administrator Userrole has the module role user in the administration module.
This should be set to the module role administrator:
I have changed the settings accordingly (see screenshot), but still the same error:
Not sure if this will help, but you can try setting entity access to yes in the create user microflow.
I have added a new Role Collection "Test" to the subaccount:
Then I have added this "Test" Role collection to the Administrator role:
However, I still get the same error when deploying and running the Mendix app. Did I miss something?