I have not had any problems installing Enterprise apps on the iOS 13 betas from a web server.
We have the same problem.
The issue is, that the enterprise developer profile is not created in settings/profiles in iOS 13 Beta
reproduce the error:
1. Download & install InHouseApp via Web with manifest file in iOS 12
2. Enterprise Developer profile is created
3. Trust them
4. Start the App -> it works
5. Update to iOS 13 Beta
6. App and profile are already on the phone
7. App start -> it works
8. Reinstall App in iOS 13 Beta (such Point 1.)
9. Get the error "App could not install. Try later". The icon is on the screen, enterprise profile is already in the settings
10. App start -> Not works -> error message (such Point 9.)
11. Unistall App & delete enterprise developer profile
13. Download & install App (such Point 1.)
14. Same error (Point 9.)
15. Settings / profile -> no enterprise developer profile
The issue is, that the enterprise developer profile entry is not be created,
so I can not trust and this the reason (I thing so) why starting the app not works.
Perhaps it is an issue only in the beta versions?
Can somebody else approve the issue?
I've found a solution. I read in the documentation https://help.apple.com/deployment/ios/#/apd11fd167c4 that the URL in the manifest file for the ipa file should be a fully qualified url. I my case I return the ipa file via an webservice, in my opinion that is not an fully qualified url for the ipa file.
Now I publish the ipa directly on my websever. No it works