CriticalPDF

Troubleshooting

Fixes for the most common CriticalPDF install and runtime problems.

MSI install fails with error 1920

Service ‘CriticalPDF Service’ failed to start.

Cause: The service was installed but couldn’t start during the MSI’s verification step — usually because the install folder couldn’t be written by LocalSystem, or another service is bound to the loopback port the management API needs (default 127.0.0.1:9100).

Fix:

  1. Cancel the install.
  2. Confirm nothing else is listening on the management port: 
    Get-NetTCPConnection -LocalAddress 127.0.0.1 -LocalPort 9100 -ErrorAction SilentlyContinue
    If a previous broken install left a process bound there, kill it.
  3. Re-run the MSI.

If you need a different port, edit TcpPort in serviceconfig.json after install and restart the service.

Service won’t start — error 1053

The service did not respond to the start or control request in a timely fashion.

Cause: The service started but failed before the SCM heartbeat. Usually a corrupted serviceconfig.json, a permission problem on the InProcess / DeadLetter folders, or a missing bundled-runtime file.

Fix:

  1. Check the latest log: 
    Get-Content "C:\ProgramData\CriticalPDF\logs\criticalpdf-service-*.log" -Tail 50
  2. If you see JSON parse errors, validate C:\ProgramData\CriticalPDF\serviceconfig.json in a JSON linter and fix the syntax.
  3. If you see permission errors, make sure OutputFolder and OnFailureFolder from the config are writable by LocalSystem.
  4. If you see runtime not found, run a Repair from Settings → Apps → CriticalPDF Suite.

CriticalPDF printer not appearing in print dialogs

Cause: The printer queue was removed, or the spooler is wedged.

Fix: The service recreates the queue on its next health check. To force it:

Restart-Service "CriticalPDF Service"

If the printer still doesn’t appear after a restart, check for driver-package corruption:

pnputil.exe /enum-drivers | Select-String CriticalPDF

If nothing comes back, the driver was removed by something. Run a Repair from Settings → Apps → CriticalPDF Suite.

Captures count up, but nothing reaches the destination

Cause: The service captured the print but the desktop app isn’t receiving or processing the handoff. Common reasons:

  • No user is logged in to receive (jobs go to the dead-letter queue, will replay on login).
  • The desktop app crashed or isn’t running.
  • A template error is rejecting the capture.

Fix:

  1. Open Help / Support → Service status (advanced) in the desktop app. Check Last handoff — if it’s recent, deliveries are working and the dead-lettered jobs are older.
  2. Check Last dead-letter and Service stats (advanced) → Dead-letter queue on disk for backed-up captures.
  3. Use Recent log (in-memory) to watch new captures in real time — filter by WARNING or SEVERE to spot template errors.

Email deliveries fail right after they used to work

Cause: OAuth refresh tokens were revoked (most often: the user changed their Google or Microsoft password), or the SMTP server rotated credentials.

Fix:

  1. Settings → Email Settings → Test connection. The error message points at the specific failure.
  2. For OAuth providers: re-pick the provider and walk through the consent flow again — it’ll issue a fresh refresh token.
  3. For Custom SMTP / Computer Team Inc.: update the password and Test connection again.
  4. Once the new credentials are stored, dead-lettered jobs replay automatically on their next retry cycle.

”License key already in use on another machine”

Cause: The seat is consumed by an old or decommissioned install.

Fix:

  • If the old machine is reachable: open CriticalPDF there → Settings → Licensing → Release license.
  • If it’s gone: email sales@criticalpdf.com with the license key and we’ll release the seat from the server.

Dead-lettered captures unrecoverable after EncryptionPassword change

Cause: Captures in the DeadLetter folder are sealed with the previous EncryptionPassword. Changing the key (intentionally or via a reinstall) makes existing sealed files unreadable.

Fix: there isn’t one once it’s done. To avoid this:

  • Drain the dead-letter queue (replay all pending jobs) before rotating the key.
  • After rotation, anything still in DeadLetter is gone.

Send diagnostics

The single best way to get a fast response from support:

  1. Open Settings → Help / Support → Diagnostics.
  2. Click Send diagnostics to support.
  3. Review the staged zip in Explorer (it’ll show you what’s included).
  4. Confirm — your default mail client opens with the zip attached and the subject pre-filled.

The bundle contains the last 14 days of service logs, recent app logs, a copy of the configuration with known secret fields redacted, an environment summary (Windows version, suite version, component versions), and the last 100 Windows Event Log entries from the CriticalPDF source. It does not include OAuth tokens, SMTP passwords, license keys, PDF encryption passwords, or serviceconfig.json.

Still stuck?

Email support@criticalpdf.com with the diagnostic bundle attached. We typically reply within one business day.

Was this page helpful? Let us know.