Are you plugged into shore power and already fully charged?
Have you ever seen the display read anything but zero?
Here is the manual, ensure the display is in the correct mode. It looks like it is tho, displaying solar output.
The troubleshooting chart in the manual indicates no data as an issue with the display cable. You could try unmounting the display, bringing it near the charge controller and connecting it with a different telephone cord. Manual says you can use any standard phone cable.