I’ve been struggling these last two weeks in seeing what the issue was. I’m seeing activity errors in my queue item activities (referencing the old Enterprise Queue Item and not the Core Queue Item type) even after uninstalling 20.4.1 Studio/Robot with 20.10.2 Studio/Robot. I even re-created my process from scratch, taking the 20.10.2 REFramework Template.
Once I recreated the process, making sure the Queue Items being used are referencing the Core.QueueItems type, I’m able to successfully publish my package to the Orchestrator (20.10). However after saving and closing the process in Studio. When I try re-opening, all my activities that reference the Queue Item type become invalid, and even my arguments for the Queue Items reference the old Enterprise type, not the Core type.
My temporary solution was to delete the project.json and reopen the Main.XAML file. Interestingly enough, all the queue item types went back to the right updated type from the UiPath Core Activities. HOWEVER I noticed that my Alteryx Activities package was no longer present. (1.0.3)
When I tried to reinstall the Alteryx package, my missing activities related to Alteryx became valid and visible again and I was able to publish the whole project to Orchestrator. But then after reinstalling Alteryx packages, and closing the whole studio. I tried to open the Main.xaml file again. That time I got the missing errors again attributed to the old Queue Item types.