I'm the owner of my Azure Portal Subscriptions and also my DevOps Portal Organizations also. But I'm not getting the Azure Subscriptions while creating service connection in Azure DevOps Portal.
I tried Googling and applying some of the steps like
- checking the access of subscription, app registration,
- https://learn.microsoft.com/en-us/troubleshoot/azure/devops/issues-service-connection-task#unable-to-see-the-azure-subscriptions-while-creating-a-service-connection-even-after-having-the-necessary-permissions
- You don’t appear to have an active Azure subscription when creating new Kubernetes service connection in Azure DevOps
etc. but no luck

Converting my comments as answer:
To fix the issue
You don’t appear to have an active Azure subscriptionwhile creating service connections in Azure Devops, troubleshoot using the below steps:Check 1:
Switch Directoryand Select Default directory.Check 2:
Security details should be in
disabledstate.disabledor not. If this optionEnabled, change it todisabled