Ensure that Microsoft.CognitiveServices is not only registered but also fully active in your subscription.
Under Azure Portal > Subscription > Resource Providers and make sure that Microsoft.CognitiveServices is registered.
The service might not be available in the region you’re attempting to deploy.
See:
https://azure.microsoft.com/en-us/explore/global-infrastructure/products-by-region/
Make sure Firewall is not blocking the service.