One Coaxial Outlet Working

They're probably disconnected from the main splitter, or there is no splitter at all. See if you can trace the lines back to a central location and see.

That's a great question @user_973bcf! As EG mentioned, the other outlets may not be connected to the main splitter outside the home. 

In many homes, technicians activate the outlet that will be used for the installation, typically one in a central location to help provide the best WiFi coverage throughout the home. As a result, other coax outlets may not be connected to the active line or may not be part of the current splitter configuration.

Are you looking to relocate your modem to a different room, or is there another reason you're trying to use one of the other coax outlets? 

P.S. Thank you for your help, @EG! We appreciate you sharing your knowledge with the community.

YW @XfinityAldrik !