@Chris Apologies for the delayed response, the error message you are seeing indicates that the token you are using to authenticate with Azure is issued for a different tenant than the one you are trying to access. This can happen if you have multiple Azure subscriptions or if you are using a different tenant than the one you used to create the key vault.
Would suggest reviewing the following info:
Check the tenant ID: Make sure you check the tenant ID associated with your Azure account for which token is issued.
Check the subscription. make sure that the subscription ID matches the one associated with the key vault.
Verify the access policy and authentication token from the Key vault standpoint.
Let me know if the above information helps to isolate the issue, feel free to post back.