The add-on needs to be re-installed. This is done by following these steps:
If the add-in is deployed centrally, it can take a few hours for every user to get the new add-in on their Outlook desktop client.
Please read through the requirements! There is most certainly some requirement that is not fulfilled.
If using Exchange 2013, you might get this error due to different internal/external EWS URLs. Steps for troubleshooting is found here: https://blogs.msdn.microsoft.com/emeamsgdev/2014/09/19/troubleshooting-exchange-2013-mail-apps-executeewsproxy-calls/
If the offical mail address in Outlook does not correspond to the mail address in Lime (email field on coworker card) the activation will not succeed.