To followup. I tried this on another site. Same issue. There is a problem with upgrading. It's not anything to do with Laravel. I ran composer update on this site before adding the updated Grocery. It worked fine. Once I add the updated zip file to artifacts and run composer update, it fails with the message above. Unfortunately, it doesn't log anything. I need to know what changed from 2.6.10 to the current to figure this out.
That's very weird! Can you please send me some more details on firstname.lastname@example.org (e.g. screenshot, your controller and/or a public URL) so I can have it also a look?