This might be related to the type of volume licence you have with Microsoft.
Microsoft have removed support for Internet Explorer 11 and, as a result, Ezekia was updated to remove IE11 components now that it is no longer supported. However, it turns out that Microsoft are still using IE11 embedded inside their volume licencing software. This means that the Outlook add-in does not load.
We don't know if or when Microsoft plan to patch their volume licenced products. In the meantime, the recommended solution is to switch from volume licencing to Business Premium or E3 licences. This will allow your IT team to upgrade you to the latest MS365 clients and install the all-important WebView2 software that replaces the old IE11 component that prevents the add-in working.