Unable to Create AzureFileShare Protected Item in Vault

### Issue Details
Unable to create a Backup item for a new Premium Files share. Get an "Microsoft Azure Backup encountered an internal error." when executing via ARM template. In a supporting region ie canadacentral, eastus and can do it via Portal. Use the same template the Portal created/used to create the Files backup item so at a loss on what the issue is - suspect that it's to do with the registering/caching that Portal mentions it's doing - perhaps https://docs.microsoft.com/en-us/azure/backup/backup-afs-cli#enable-backup-for-azure-file-shares?

### Repro steps (*if necessary, delete otherwise*)
1. Premium Azure Files storage account + File Share created
2. Recovery Vault created
3. Vault Backup policy created
4. Attempt to create backup for Azure File share fails with "Microsoft Azure Backup encountered an internal error."
5. Deployed to canadacentral + eastus - supports Premium Files + Backup
6. Works successfully via the Portal - assume it has something to do with the Vault "registering" + refreshing itself according to the activity log

Find attached template to reproduce.
[azurefiles-vault-backup.json.zip](https://github.com/Azure/azure-quickstart-templates/files/4209824/azurefiles-vault-backup.json.zip)

Any help appreciated.

Start with the attached azurefiles-vault-backup.json.zip and follow the listed five-step reproduction using a Premium Azure Files share, Recovery Vault, and backup policy. Compare the ARM-template deployment with the Portal-created template and review activity-log behavior around vault registration and refresh. Done means isolating a reproducible template or service difference and documenting a confirmed fix or escalation.

Written by the indexing model from the issue text.