Mounting Azure Blob Storage Container using Fabric Notebook (PySpark)

I'm attempting to mount an Azure Blob Storage Container within a Fabric Notebook as suggested here.

I am setup as a Storage Blob Data Contributor on the container (which I have seen suggested).

The code:

from notebookutils import mssparkutils  

accountKey = mssparkutils.credentials.getSecret("<vaultURI>", "<secretName>")
mssparkutils.fs.mount(  
    "abfss://<mycontainer>@<accountname>.dfs.core.windows.net",  
    "/test",  
    {"accountKey":accountKey}
)

I get an error: "Mount failed with operationId <operationId>, get detail from /var/log/blobfuse/blobfusev2.log"

When checking the log, I notice the following sequence:

|2024-02-28T17:44:15.982905+00:00 vm-65b06715 blobfusev2[2878]: Testing authetication to /<some-guid>/test/ ...

|2024-02-28T17:44:16.036071+00:00 vm-65b06715 blobfusev2[2878]: Unknown failure: [json.exception.type_error.302] type must be string, but is number

|2024-02-28T17:44:16.036174+00:00 vm-65b06715 blobfusev2[2878]: Failed to connect to the storage container. There might be something wrong about the storage config, please double check the storage account name, account key/sas token/OAuth access token and container name. errno=1600

Naturally, I have double-checked the accountname and key as well as tried other methods like using a sas token.  So far, I'm have no success mounting anything (I also tried mounting a lakehouse but it just times out with no errors in the log).  Am I missing something?