The ribbon button is missing

Installed the add-in, but there is no button on the Home tab?

1. Close Excel completely and reopen it. The ribbon sometimes only picks up new add-ins after a restart.
2. Go to Home > Add-ins > More add-ins > My Add-ins (or Insert > Get Add-ins) and open it from there once. After that the ribbon button sticks.
3. On a work account, your IT admin may need to approve store add-ins first. If the store page shows an admin notice, that is the reason.