Media player has stopped working properly

Recently, the banner that usually appears when playing a video with Firefox (such as from youtube.com) has stopped appearing. I also cannot pause or play a video by clicking the controls on my headphones, which used to work. And finally, when playing a video or song from another app (eg. Newpipe), the video on Firefox does not automatically pause, which it used to to. I've tried updating both the app and my version of Android, but neither have helped. I would add images demonstrating what the media banner used to look like, but the "Browse" button simply does not work. Please help