Cannot create metaobjects with app-owned type

GraphQL Admin API Troubleshooting
1

We’re trying to create app-owned metaobjects to be able to store and query some customer data, however when we run metaobjectUpsert or metaobjectCreate to create a metaobject with a type starting with “$app:”, we get the following error (tried both from GraphiQL and from a local script):

Not authorized to modify entries of type “app–174649278465–membership_expiration”

Here is the metaobject definition that we create using the same app that we use to try to create the metaobjects.

[
    {
      type: '$app:membership_expiration',
      displayNameKey: 'customer_id',
      name: 'Membership Expiration',
      description: 'Tracks membership expiration dates for customers without payment methods',
      access: { admin: 'MERCHANT_READ', storefront: 'NONE' },
      fieldDefinitions: [
        {
          key: 'customer_id',
          name: 'Customer ID',
          description: 'The ID of the customer',
          type: 'single_line_text_field',
          required: true,
        },
        {
          key: 'expiration_date',
          name: 'Expiration Date',
          description: 'The date when the membership expires (YYYY-MM-DD)',
          type: 'single_line_text_field',
          required: true,
        },
      ],
    },
  ]

Creating the definition works as expected without any errors. When we query the createdByApp { id } field from the metaobject definition and currentAppInstallation { app { id } } they both return the same app prefix. We have added read_metaobjects and write_metaobject_definitions to the scopes.

What would be the next steps to debug this issue? How do I know what is causing my app not being authorized to access its own metaobjects?

Thanks for your help.