@Phil Evans - Thanks for bringing this to our attention.
It is not normal for the registration process to take hours. The registration process usually takes a few minutes to complete. If the registration process is taking longer than expected, it could be due to a service outage or an issue with the Azure portal.
You can check the Azure status page to see if there are any known issues with the Azure HDInsight service. When I checked there has been no known issues, you can try unregistering and registering the provider again after some time or you can try to register resource provider using other methods like Azure PowerShell or CLI.
For more details, refer to Azure resource providers and types.
If the issue persists, please do let us know. We will be reaching out to the product team and they will be able to investigate the issue and provide you with a resolution.
Looking forward for your response.