Can take pics, but no video, on Pi 3B+

I just installed Astroprint on a new RPi3B+ and video streaming works fine with Chrome on my computer, but video streaming won’t work with the Astroprint App on my iPhone. I can still take still pics with the App, but no video. I get this error message: “Camera Error, Error in device’s video system communication. Please restart the device.” I have restarted the Pi multiple times and no difference.

Interestingly, everything works fine with the RPi 3 that I also have a 2017 version of Astroprint running on. The App on my iphone works fine with still and video with the exact same camera!

Any ideas?

This is likely due to network problems delivering WebRTC Video. Here’s more info about the required network configuration:

Thanks Daniel. Read through that but I don’t see how that could explain that everything works fine when I plug in my AstroBox gateway made with a pi3b using the same network and everything, but won’t work with the pi3b+.