joshua1zn's solution helped me as well: Created an empty project in latest 2018 version Unity where I added the IAP package and enabled the IAP service, then copied over the files from the 3 plugin directories to the 2019 project. The only difference I can see from source control is that Plugins\UnityPurchasing\Bin\Editor.dll and Plugins\UnityPurchasing\Bin\Stores.dll have now been added as new files (I also see a few guids changed in metafiles, but i guess that was due to something else). The "Update API, did you make a backup first" popup didn't show for me either even though I had no console errors prior to importing the IAP package. I also removed and re-added the IAP package and removed the plugin files prior to importing them again. Please investigate this, it was yet another very annoying and confusing bug in Unity. It doesn't make sense to me why VR is referenced here when there's no VR package or code at all in the project.