“Token does not exist” or sudden 401s from Linnworks: what happened

Short answer: the app's install token has been invalidated — usually because the app was uninstalled, permissions changed, or credentials were rotated.

What invalidates a token

Uninstalling and reinstalling the app in Linnworks. Changing the application's permission scopes. Regenerating the application secret. Occasionally, account-level changes at Linnworks' end.

Restoring access

Reinstall the app from Linnworks Settings → Apps, approve the permissions, and capture the fresh install token from the redirect. Then update wherever the token is stored — for self-hosted deployments that means re-setting the secret and redeploying.

Why it looks like a code failure

Auth errors often surface as generic 500s or empty results rather than a clear "your token expired" message. If everything worked and then uniformly stopped, suspect auth before suspecting logic.

Prevention

Note which integrations depend on which application, so a routine reinstall does not silently break three tools. Full walkthrough for self-hosters: the Linnworks MCP troubleshooting guide.

Questions, or want a tool we don't have yet? Email hello@grafto.co.uk — a real person replies.