Can I assume that you are creating with the new responsive design?
If I were you, I would suspect a case where the height settings specified in absolute values are not sufficient.
Check the source in the preview screen in your browser. If the source is picking up the text you have entered, there is most likely a problem with the visibility settings, such as height and width.
If it is otherwise, suspect a case of problems with parent-child relationships, etc.
This RG is CHILD to the PAGE directly. So, it doesnt seem to be any issue wrt to Parent-Child relationship.
This RG contains 2 elements : Text (188 W x 28 H) & Input (194 W x 35 H), whose sizes are well within the size of the RG (300 W x 100 H). Also, the visibility on page load is checked for all 3 elements.
With above settings, while the RG is visible, it is not showing any elements inside it.
If so, a possible possibility is that the Type of content and Data source of the RG are not set.
Try setting a database that is not important to try.
At least I was able to reproduce the same situation as you. (Meaning it wouldn’t have shown up if you hadn’t set anything)