If version-level immutability support is enabled for a container and the container contains one or more blobs, then you must delete all blobs in the container before you can delete the container, even if there are no immutability policies in effect for the container or its blobs.
You can clear the hold and then delete the blobs. Afterwards you should be able to delete the container and storage account. More information can be found in this StackOverflow thread.
Hope this helps. Let me know if you are still facing issues or have further questions.
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