I have a RepeatingGroup with Type of content = ChatMessage. When I click on Data source → Do a search for, the dropdown shows “No results found” and I can’t select ChatMessage. The field stays blank. How do I fix this?
Probably reload the page or browser for a start
Can you share a screenshot please so we see what you are talking about? 
Did you check the data source of the parent group/container?
If it isn’t receiving the expected data, the child elements won’t display the correct information.