Hi,
What's your make and model of amp?
I have probably asked this question many times before, on various threads, but, it always helps to state make and model when you ask about an issue.
If it happens to be a Denon (and most other makes) - look at the HDMI pass-through setting.
Please, if it works, respond so that other users aren't left hanging to know if that was the solution.
Cheers.