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Expired certificate – Outlook Add-in application fails to start

This article applies to Microsoft Office Add-ins:

  • Messageware SERT 
  • Messageware Mail Forms 
  • MessageWare Message Save 

SUMMARY

When the certificate that is being used for the Office Add-in website expires, the Add-in is unable to start.


SYMPTOM

Sometimes when trying to launch an Office Add-in the application will not start and the following message appears: "Something went wrong and couldn't load this app. Please try again later"

Messageware Add-ins (Outlook Add-ins/Office Add-ins) run under the Default website in IIS. The Microsoft architecture for Add-ins blocks access when the certificate is expired. The Add-in framework does not trust the website and will not load the app. 


RESOLUTION

To resolve this behavior replace the expired certificate with a valid one on the server where the Outlook Add-in is running following the instructions below.

Step 1: Import a Valid Certificate:

  1. Copy a valid certificate to a temp folder on the server where the Outlook Add-in is running from 
  2. Double click on certificate to import it and select the 'Local Machine' or 'Store Location'
  3. Enter the path to the valid certificate and enter the password for the 'private key' when prompted
  4. Choose 'Automatically select the certificate store based on the type of certificate' and select Next
  5. Click 'Finish' to complete the import 

 

Step 2: Update the web site certificate in IIS:

  1. Launch the IIS Manager and navigate to the Default Web Site
  2. Click Bindings on the right pane, under 'Actions'
  3. Click on 'https' and click the drop down under 'SSL Certificate'
  4. Choose the valid certificate and click OK