Welcome to the forum!
If you don't have a copy, you can download the owner's manual from Marantz in PDF format at this link
here.
When you set the sound mode to Audio EX 2, the display will turn off. However, are you saying that the remote can't perform any operations? Try hitting the "Dimmer" button on the lower left of the remote and see if the display on the Marantz shows up for about three seconds (page 26 of the manual).
Also, troubleshooting issues with the remote not working is discussed on page 50. Try hitting the "CD" button near the top of the remote to see if that works.
