@armond_in_hj - By "FIOS box", I believe the OP is referring to the ONT.
@OP - Not clear what you're referring to as the "FIOS box". ONT? STB? router?
You can't have coax WAN and ethernet WAN active on the ONT at the same time.
Can coax and cat5 be active at the same time
You best solution is a MOCA LAN adapter as armond_in_nj has suggested.