No audio on Facebook, YouTube Android app when on 4G

My Pixel 5 audio is working while on WiFi at home. When I'm not on WiFi and using 4G, any video on Facebook or YouTube has no audio. On Facebook I can turn the audio off and on for each video, doing so makes no difference. I can't see volume controls anywhere in the YouTube app, either on each video, or in the app settings. In Android Settings > Audio, all audio levels are high. Why would audio not work on any Facebook or YouTube videos while on 4G? The problem has followed me to a new Pixel 6a too.