As a first step to resolve the issue, try re-registering the resources like Compute, Network. Try deleting the AKS cluster again after the re-registration. You can try re-registering the resources by visiting Subscription > Settings > Resource Providers as shown below
Select microsoft.network and microsoft.compute and re-register these resources
Let's know, if it helps. Otherwise, we need to dig further and see what is stopping from deleting the resources
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