I am assuming that this car has the standard Halogen headlamps & not the HID or LED? If it can turn on the blue hi-beam icon in the cluster, I would say that the headlamp & dimmer switches are OK.
The BCM (body control module) controls the left & right-side hi-beams separately, each with their own wire. So what is happening with one side is also happening to the other.
See the red arrows on the wiring diagram (Wt/Gn & Wt/Gy wires) below. Both headlamps have separate grounds (four Bk wires each) at G915A &G906A. Again, it would be unusual for both sides to fail at the same time, but corrosion happens & we need to rule out the more common, simple things first.
Is there power at pin #6 at the headlamps w/ the hi-beams on?
The BCM can put itself into 'protection' if it thinks that there is too much current draw (a short). Instead of blowing a fuse, it will shut off power on that wire until the short condition is lifted. It may need a higher-functioning scan tool than an OBDII engine code reader and needs a tool capable of reading body codes.
Possible Hi-beam fault codes: