This error message appears when the Crossware application (or extension manager hook) is not being correctly loaded by the domino server. This error usually occurs for two reasons:
1. The domino server has not been restarted after the installation. The domino server only loads extension manager applications when the server starts.
2. There is a problem with the installation. These errors can be dependant on the OS used.
Steps to resolving issues
1. Check the server has been restarted. See How to confirm if the Crossware Mail Signature application has loaded to check that the application has been loaded correctly. You should see the Crossware copyright message.
2. Confirm the notes.ini settings are correctly updated. See How to Check the Extension Manager Hooks to verify what has been set in the notes.ini.
3. If you are running Domino 8.5.1, there is a known issue with this release that affects 3rd party applications.
4. Users on the IBM i platform will need to check that the ICU libraries are also installed correctly. Please see AS400 Install Unicode Libraries and Error loading Unicode for more information. Also check the links are correct How to check the iSeries Links.
If none of the above helps, please contact Crossware technical support. Please email the domino version, OS and Crossware mail signature version to firstname.lastname@example.org and the team will be able to help.