You are facing this message all the time even if you've followed the installation guidelines?

Steps to resolve

1. Remove skybow Add-In Foundation from your site
2. Remove the corresponding skybow product (skybow rich forms, skybow theme designer, skybow list view search, skybow action links, skybow tabbed pages) from your site
3. Delete hidden document library -> put the url manually in your browser
   1. if Rich Forms -> [yoursiteurl]/FormsStoreLibrary
   2. if Theme Designer -> [yoursiteurl]/sbThemeDesigner
   3. if List View Search -> [yoursiteurl]/sbListViewSearch
   4. if Action Links -> [yoursiteurl]/sbActionLinks
   5. if Tabbed Pages -> [yoursiteurl]/sbTabbedPages
4. Delete the Add-Ins and the hidden library as well in the site collection recycle bin (second stage as well)
5. Remove free license from your SharePoint Admin Center
   https://yourtenant-admin.sharepoint.com/_layouts/15/TA_AllAppLicensesManagement.aspx
6. Download the corresponding full trust version from the skybow portal
   /hc/en-us/sections/360003398160-Release-Notes-Downloads-SharePoint-Add-Ins
7. Unzip the package and upload the .app file to your app catalog
   https://yourtenant.sharepoint.com/sites/appcatalog/AppCatalog/Forms/AllItems.aspx
8. Add the app from step 7 again to your site and upload the license key
9. (Optionally delete the skybow Add-In Foundation from your app catalog, it's not needed anymore)

You're done, the Add-In should now work like a breeze, otherwise let us know that we can help you out.