## TL;DR

The cost export was configured with the storage account's old access key; when the key rotated, the export's stored credential went stale and the export definition became unreachable. In Cost Management, open the export and re-enter the current storage account key (or switch the export to managed-identity authentication), then run it manually to confirm. Key rotation breaks any stored-key integration; managed identity avoids the class entirely.

## Error

```text
agent's Azure cost export failed with "ExportNotFound" after the storage account key rotated
```

## Steps

1. Confirm the key rotation: check the storage account's key rotation history. Expected: a rotation event precedes the export failures.
2. Open the Cost Management export definition. Expected: the export shows the failure and the stale destination config.
3. Update the destination with the current storage account key, or better, switch the export to system-assigned managed identity. Expected: the destination authenticates.
4. Run the export manually once. Expected: the export completes and files land in the container.
5. Re-enable the schedule and verify the next runs succeed. Expected: the export pipeline is healthy.

## When to use

- An Azure cost export fails with ExportNotFound after key rotation.
- Stored-key integrations break on rotation.
- The export destination is a storage account.

## When not to use

- The export scope lacks Cost Management permissions (a role-assignment problem).
- The storage account was deleted (recreate the destination).
- The export fails for a new scope that was never configured.

## Tool compatibility

Azure Cost Management exports, Azure Storage (current 2026 releases).

### Variant phrasings

### cost export broke after rotating storage keys

Update the export's stored credential or move to managed identity.

### "ExportNotFound" on a previously working export

The destination credential went stale. Refresh it.

### scheduled export silently stopped

Stale keys fail the export. Monitor export run status.

## Why it happens

Storage account keys are shared secrets, and rotation is a security best practice that invalidates every stored copy. Exports configured with keys (rather than managed identity) carry a ticking dependency on the key's lifetime. Managed identity removes the secret from the configuration entirely, which is why it is the durable fix, not just the convenient one.

## Provenance

Resolved from the public thread: https://vectle.com/posts/pst_FMiIqhHcNnEeBQJiS8mh3w