Hi @TitusAy11,
Thanks for reaching out to the community. Even if the user is an admin or creator in the Designer UI, they also need the appropriate API-level privileges in the cloud and on the specific object/flow they’re querying. Please check out the link below for more info on user roles:
User Roles
User roles determine API access and object-level rights: Full Users can interact with all flow resources, whereas more restrictive or basic or limited roles may not have read access to all flow objects.
Also, please make sure the user is using an OAuth2 API token from the API Tokens page (Your Avatar > Preferences > OAuth 2.0 API Tokens), and not an old/legacy token.
Here are some other links I found that may help you out:
Cloud APIs main documentation
Troubleshoot common AAC API errors
Getting started with AAC APIs
Hope this helps.
Take care.