## TL;DR
Acronis backup failed with error is a banner over a specific module error in the activity details. Open the failed activity, read the module and error code lines, and fix that layer: VSS writers, plan credentials, destination space, or the agent service. The banner alone never tells you which, so always work from the detailed log entry.

```text
acronis backup failed with error
```

## Use this when
- An Acronis Cyber Protect plan shows backup failed with error.
- The activity list shows a red failed entry with a details link.
- The same machine backs up after a reboot but fails again days later.

## Not for this skill when
- Veeam or Commvault shows a similar banner. Their logs and codes differ.
- The Acronis agent is offline entirely. That is a connectivity problem first.

## Steps
1. Open the failed activity details and record the module, error code and the first cause line. Verify: the specific Acronis error is captured, not just the banner
2. If the code points at VSS, check writers on the machine with vssadmin list writers and restart failed writer services. Verify: writers return to stable
3. If the code points at access or credentials, re-enter the plan credentials and test the destination path from the agent machine. Verify: the agent can open the destination with plan rights
4. If the code points at space or write errors, check destination free space and storage health. Verify: space and write tests pass
5. Rerun the plan and confirm the activity completes with a success entry. Verify: the plan produces a new recovery point

## Variant phrasings
### acronis cyber protect backup failed error code
The error-code focused phrasing.
### acronis backup plan failed details
The activity-log variant.
### acronis agent backup error module
The module-code wording.

Compatibility: Acronis Cyber Protect 15 and Cyber Protect Cloud agents on Windows and Linux, with local, network and Acronis Cloud destinations.

## Why it happens
Acronis wraps many subsystems under one plan result: snapshotting, source reading, compression, destination writing and cataloguing. The banner reports only that one subsystem returned an error, while the activity detail carries the module number that identifies it. Reading the detail first turns a vague failure into a short, known fix list.

## Edge cases / pitfalls
- Recurring VSS module errors after Windows updates are common. Check writer state before reinstalling the agent.
- A plan edited to a new destination keeps old credentials in some tasks. Re-save every task in the plan.
- Agent service stopped by endpoint protection shows as backup errors, not offline, if the management server still has a recent heartbeat.

## Provenance

Resolved from the public thread: https://vectle.com/posts/pst_cB_JvbgO9_kbW0ERbttz3w