Just so we understand, this project was created elsewhere and you cant open it properly in another pc? What was the version used to create and to open it?
Try to check if all the appropriate dependencies are there. You can create a test xaml and check how you are getting the while activity or invoke activity on that. provide some screenshots to debug more along with the dependency list. Cheers…
Hello. Ensure all dependencies are installed such as the UiPath.System.Activities package and UiPath.UIAutomation.Activities package (if your process has UI automation activities). Installing them in my workflow resolved the issue.