Mammoth error messages: what they mean and how to fix them

General error messages

Sign-in and permission errors

Sign-in or API credentials rejected (401)

Your session or API token is invalid, expired or missing, so the request is refused with HTTP status 401. In the app, Mammoth first tries to renew your session. If that fails, sign in again.

1. Sign out and sign back in.
2. If you use two-factor authentication, check that the time on your authenticator app is correct. See Security.
3. If you forgot your password, reset it from the sign-in page. Asking for too many resets shows "Password reset limit reached. Please try again tomorrow".
4. For API calls, check that the token is sent and hasn't been revoked. See API errors.

"You lack the necessary permissions for this action. Please contact your admin for assistance." (403)

You're signed in, but your role doesn't allow the action, so the request is refused with HTTP status 403. Some screens show the shorter "User lacks permission" or "You don't have permission to modify this item."

A feature your plan doesn't include shows a premium icon and an upgrade prompt, or asks you to contact the Workspace Owner, instead of this error. See What happens when you reach a plan limit.

A connection's key expired

Credentials for an external source stopped working: an OAuth sign-in expired, a password changed at the source, or an API key was rotated. The connection shows Error, and the Connectors launcher lists it under Needs attention with key expired. Open it and use Edit connection to sign in again or enter the new key. Only a Project Admin can repair a connection ("Only a project admin can repair this connection."). See Fix connection and refresh failures.

File upload error messages

You can't add or replace data in a dataset with a ZIP file that holds more than one file. See Add or replace data.

Characters look garbled after upload

The file uses a character encoding other than UTF-8, so accented or special characters appear garbled. Save the file as UTF-8 and upload it again. In Excel, use Save As and choose CSV UTF-8 (Comma delimited).

Dates or columns are read wrongly

If Mammoth can't tell whether dates are day first or month first, the dataset's panel asks Which way round are these dates?. If columns appear merged, open How it was read to set the delimiter and header row. See How Mammoth reads your files.

Errors when adding data to a dataset (schema errors)

When you add data to an existing dataset, the dataset's If column type doesn't match and Column mapping settings decide what happens to columns that differ. See Add or replace data.

Pipeline task error messages

When a task fails, the pipeline shows This pipeline has errors with "Fix the failing tasks to continue", and the failing task is outlined in red with its message. Start with the first failing task: later tasks often fail only because an earlier one did. See Fix a failing step for each kind of failure.

Math Function and date format errors

A Math Function expression that can't be read shows a message such as "Column Revenue is missing" or "Syntax error: unmatched brackets". See Fix a failing step. A date format Mammoth can't use shows "Format for date is invalid. Select a valid date format".

A join returns no rows or too many rows

No matches usually means the key values differ in case, spacing or type. Too many rows means the key has duplicates: Mammoth warns "Key column(s) have non-unique values". See Fix a join that returns zero rows and Fix a join that returns too many rows.

Automation error messages

A failed automation shows Error, and Last run result in its detail panel gives the reason. Fix the cause, then use Run now. Mammoth doesn't retry a failed run on its own. See Manage automations.

A file whose columns don't match a Data Consolidation's destination doesn't fail the automation. It shows Files not added instead.

Plan and storage limit messages

See Limits and quotas for each plan's allowances.

Dashboard error messages

For blank or stale dashboards, see Fix dashboard problems.

Trash error messages

API rate limit: "Rate limit exceeded." (429)

You sent too many API requests in the current one-minute window. The API answers with HTTP status 429, the message "Rate limit exceeded." and a Retry-After: 60 header. Wait the number of seconds in Retry-After, then send the request again. If you keep hitting the limit, spread requests out or batch them. See API rate limits and API errors.

import time
import requests

def api_call_with_retry(url, data, max_retries=3):
    for attempt in range(max_retries):
        response = requests.post(url, json=data)
        if response.status_code != 429:
            return response

        # Wait as long as the server asks (60 seconds by default)
        wait_time = int(response.headers.get("Retry-After", 60))
        time.sleep(wait_time)

    return response  # Final attempt

When to contact support about an error

Contact support@mammoth.io when an error keeps coming back after you've tried the fix, when you see "Runtime error. Contact support for help.", or when results look wrong after a transformation. Include:

1. The exact error message, copied from the screen
2. What you were doing when it appeared, and the steps to reproduce it
3. The workspace, project and dataset or View names
4. When it happened, and any recent changes you found in the Activity Log

Related

• Fix connection and refresh failures: what to do when a connection shows Error or a refresh fails.
• Fix a failing step: the full fix for each pipeline task failure.
• Limits and quotas: the sizes and plan allowances behind many of these messages.
• Add or replace data: the column mapping settings behind schema errors.
• Troubleshooting: the diagnostic checklist and how to contact support.