Radar Source Not Found on Split Screen

We have a newly installed Raymarine MFD (aSeries). Both chart and radar seem to work fine on single pages (and as an overlay). However, when viewed on a split screen, every attempt to power up the radar results in an error message "No Radar Source Found." Any suggestions?

Also, our 20-year-old Raytheon calculated ETA to waypoint. Anyway to get that data displayed in a databox? Currently databoxes are set up to display SOG, COG, and DTW. I can certainly calculate ETA from those, but having it displayed for me would be nicer!

Thanks in advance.

Camelot