Hi Dave,
ARCHICAD 19 added a new function to put enhanced data into BIMx hypermodels. In this case the option which includes or excludes this data is most likely not set in the particular publisher set you are using.
Visit the Publisher set and click the little white arrow near the top of the publisher to take you up a level where you can see the names of all of your publisher sets. Highlight the Publisher Set that you are exporting to BIMx and then click Publishing Properties. In the Publisher Set Properties window that appears look for the Info Set option and change it from Undefined to one of the other options (None, Legacy, Tags and Categories, BIMx Info or other Schedule). To learn about this feature and the data that is included see this video:
I'll bring your post to the attention of our product team to let them know the current warning is not clear.
Best regards,
Nick