One of the recent and most frequent issues faced while upgrade is that of the existing Dynamics 365 For Outlook 2016 setup which doesn’t connect to D365 v9.
Right after the environment upgrades to v9, D365 For Outlook’s older version doesn’t connect.
But that’s not the end of the story, obviously, there’s is an upgrade. So let’s see how to go about this process and why this happens.
When you’re trying to re-enter credentials or connect to D365 v9 from the existing D365 For Outlook version, you see this error
The reason is that D365 version 9 required TLS 1.2. Detailed explanation of which you can find here – https://support.microsoft.com/en-in/help/4054414/dynamics-365-for-outlook-update-for-version-9-0?LCID=1033
You can either choose to upgrade to D365 For Outlook v188.8.131.52 which you can download from here – https://www.microsoft.com/en-us/download/confirmation.aspx?id=56327
Or, if you don’t have any pre-installed version, you can also directly setup D365 For Outlook – https://www.microsoft.com/en-us/download/details.aspx?id=56972
Make sure you have upgraded your D365 to v9 first. I’ve posted a related blog regarding this in the past and you can refer it here – https://d365demystified.com/2018/11/13/d365-quick-tip-higher-version-of-d365-for-outlook-wont-work-older-d365-online/
Hope this helps! 🙂