In Excel, your Smart Workpapers Add-ins should appear in File > Options > Add-ins like this:
If the COM Add-in has dropped out, add a Trusted Location to ensure the folder path is trusted for use by Excel. To do this go to File > Options > Trust Center > Trust Center Settings > Trusted Locations > Add New Location
Enter your local app data folder path (e.g. C:\Users\[name]\AppData\Local\Business Fitness) and tick Subfolders in this location are also trusted. Click OK.