I have a hunch that this is a bug, but I'll ask anyway and see if others are having the same experience.
ArcPro version 2.4.3
ArcGIS Enterprise 10.7.1
Steps:
- Created a web map in Pro. Configured the pop-up using the text option:

- Successfully tested the pop up in Pro:

- Published the entire map as a web layer (Share tab > Share as group > Publish Web Layer). Only checked the box for Map Image under Layer Type.
- Added new layer to a web map. Clicked on point and got this:

All of the dynamic fields that should be pulling from the attribute table are left blank. I checked the pop-up configuration in the Portal web map, and it looks right:

Anyone experiencing this issue? Is there a fix?