It is not obvious from your screenshot what might be the issue. Rather than setting those properties when the activity is started, you can set them when you call StartActivity. That may avoid this particular issue. You may also verify that you defined the activity not to require an Interaction. If it does, you'll need to make sure you start an interaction first.
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In our project, we had the same issue in one of our developer's OpenSpan Studio. Then we went and checked all the references with another developer's OpenSpan Studio and added OpenSpan.Events, OpenSpan.Interactions, OpenSpan.Threading .. etc. and all worked fine thereafter.