No sound on my Tonematch TS4 right headphone when you plug it in monitor (right side output)

I have a Bose Tonematch T4S that I've been using for live gig  for almost 2 years, I usually use the right side for my In-ear monitor, But last night the right side of my IEM is not working, I thought it's the IEM but when I used a different heaphones (Senheisser HD280) it also didn't work on the right side, I checked the panning, output jack, and my instruments, it's all the same. what do you think is the cause of it? anyone has the problem here? 

Thank you!

Hi hero_me,

Thank you for your post! Sorry to hear you're having this problem. 

When you connect your headphones to the T4S, are you using the dedicated headphone output on the right side of the mixer?