Adobe Premier Audio Play out issue

Hello!

I am currently experiencing an issue while working on a project that wasn't an issue until this recent update!

Usually I can use audio channels A1/2 for different videos that I used different microphones on, and alternate which audio clip I'd use by enabling and dissabling another. Currently that is not the problem. 

What is the problem is that now I am not hearing what I put into channels A3/4, which I use for background music. I can see on the audio mixer that it is playing, but even when I solo those channels I still am not hearing the audio tracks. I can hear them If I move the audio into A1/2 but that is not helpful for me. 

Would anyone know how to hear all audio channels at once? I'm not sure why this changed for me.