So I have found in my new fire tablet experience (don’t know if it’s how they are designed) but I plugged my apple wired headphones in and it didn’t work, and thought let me truly another set of headphones and they worked. The only difference in the apple and regular headphones was apple has the 3 prong jack (left, right speaker, and mic), and the other headphones only 2 prong jack (left right speaker, no microphone). So maybe if it’s headphones with a mic they don’t work. Try headphones that have 2 colored lines on the jack. Hate it cause I LOVE APPLE WIRED HEADPHONES. Side note the apple AirPods work great. Fire tablet 8 doesn’t have the best sound output