We have a custom Outlook VSTO add-in. We publish to a location which installs based on version, and it has worked perfectly for years. For some reason, the new version we pushed today is not running properly. It installs fine, it appears to be running (i.e. shows in the list of Add-Ins, has delays ignored, and shows as active) but the icon that should show up in the ribbon for a meeting is not appearing. It does work on the developer machines. No errors are logged anywhere, including Application Event Viewer. The install package does seem considerably larger, but there are no massive upgrades, and the machines with the issues have .Net 4.8 as do the development machines.