Page not found 404 error when installing Theme Designer from the office store

If you install skybow theme designer from the SharePoint store, you've added the Foundation Add-In as mentioned and uploaded a valid license.

You click on the Theme Designer app, but after loading and enabling some stuff it fails with a "Page not found" error.

To overcome this issue we advise you to install our full trust version with the steps described in this KB article

How to solve the - Install "skybow Add-In Foundation" - issue