How to reinstall the Web Service Certificate on Mac?


When installing the DYMO Software, it will also install the DYMO Web Service and the certificate it requires to run. This Web service allows web pages to directly contact the LabelWriter to perform a print job. If the Web Service did not start up properly or the certificate got corrupt, the printer may not be reachable through web pages.

Possible error messages are:

  • None of these ports were configured to use SSL certificate
  • TrustFailure (Authentication failed, see inner exception)
  • SecureChannelFailure (Authentication failed, see inner exception)
  • Could not create SSL/TLS secure channel

In that case a complete reinstall of the software and the certificate will be needed. Please perform the following steps as an administrator or from the administrator account!

  1. First, remove the printer by following article: Why am I receiving an error while printing on Mac? Do not yet reconnect the printer to the computer.
  2. Secondly, clean uninstall the software by following article: How to completely uninstall the DYMO Software?

Please note: do NOT reinstall the software before removing the web certificate as explained below.


To remove the Web Service Certificate

  1. From Finder, click on Go and select Utilities. Then proceed to find and open Keychain Access.
  2. On the left-hand side of the window, highlight System. Then select Certificates and delete DYMO Root CA (for localhost).
  3. Click on localhost if you have one available and see if it issued by DYMO. If so, please remove it also.
  4. Now empty the recycle bin and restart your computer.


Reinstall the DYMO software

  1. Perform the installation of the DYMO software using the installer. You can find the software HERE.
  2. When the installation is complete and you select Finish, a command prompt window will appear. Please click next to the Key symbol and type in your password followed by the Enter key.
    • Please note: you will not see anything typing into the command prompt, so please make sure you are typing the correct keys.
  3. Once the password has been applied, the following window will appear. Please provide your password once again.
  4. The DYMO icon will populate in the menu bar.
  5. When you click the icon, a menu will pop up. Please click “Diagnose” from the popup menu.
  6. If you receive a window with ‘DYMO Connect Service is running’, the certificate has been installed correctly.


Set up the printer again.

  1. Reconnect the power cable to the back of your printer and turn on your device.
  2. Insert your DYMO Authentic labels into the printer. Ensure that the labels are facing down and aligned completely to the left-hand side. For a visual reference, please refer to our video tutorial below:
LabelWriter 450 series and older

LabelWriter 450 series and older


Print a label

  1. Reconnect the USB cable (ensure that it is connected to the computer) or LAN cable and you are ready to print.


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