Hello, I'm not sure if you fixed or not. I have a 2022 Montana 3813 MS and this same thing happened to me. The system, called the JBL Aura Wall Mount Stereo, had the red power light on, but it wouldn't turn on. For some reason I also did not have the remote. It would not turn on with my RV as well (I've since replaced the TV with the one I had in my house). I finally called Forest River today. They gave me the name of the system and I found the manual online
here.
To fix this, open the little flip opening on the front, use a straightened out paperclip and push it gently it into the hole (this is the audio opening, but also where the reset button is). You will feel the button. Hold it down for at least 10 seconds. The power button (which should be red) should turn off. Now you should be able to turn the system on.
This information is found within section 21 of the manual.
Hope this helps.