The module azure_rm_virtualmachine has fields for plan information. Module azure_rm_virtualmachinescaleset needs to have them and forward them when creating a VM with an image that requires plan info to be specified. The CIS hardened images from the Azure Marketplace is a prime example.

subnet_name=dict(type='str', aliases=['subnet']),
            load_balancer=dict(type='str'),
            application_gateway=dict(type='str'),
            virtual_network_resource_group=dict(type='str'),
            virtual_network_name=dict(type='str', aliases=['virtual_network']),
            remove_on_absent=dict(type='list', default=['all']),
            enable_accelerated_networking=dict(type='bool'),
            security_group=dict(type='raw', aliases=['security_group_name']),
            overprovision=dict(type='bool', default=True),
            single_placement_group=dict(type='bool', default=True),
            zones=dict(type='list'),
            custom_data=dict(type='str')
        )
        self.resource_group = None
        self.name = None
        self.state = None
        self.location = None
        self.short_hostname = None
        self.vm_size = None
        self.capacity = None
        self.tier = None
        self.upgrade_policy = None
        self.admin_username = None
        self.admin_password = None
        self.ssh_password_enabled = None
        self.ssh_public_keys = None
        self.image = None
        self.os_disk_caching = None
        self.managed_disk_type = None
        self.data_disks = None