My group won't pay attention and the sessions are falling flat. What should I do?

TLDR at the bottom.

So I started playing Dnd with my friends a couple months ago. The first one to DM was one of my friends. We played their campaign and made it through and it was fun.

The next campaign I became DM. The plot was to find one of their friends who went missing after he noticed a disturbance in the forces of nature. The first session was really fun as the group entered a forest, then a town. They interacted with all the npcs really well and got into character and I was able to improvise every situation almost perfectly. They continued on with the plot and eventually fought and ogre and then got sucked into the FeyWild.

Second session I was super excited for, but when we played it, it felt disorganized and lame as they explored the fey forest. There were less characters, and the ones they did meet were weird fey people, so they didn't respond well to them at all. I didnt even get to the fight scene because we ran out of time. Everyone was just sorta distracted and it seemed like they didn't want to play.

Third session I came in with a more relaxed attitude, and I started right off the bat with a fight that was supposed to happen last session. One of the players didn't pay attention at all in combat, just being on their phone and mindlessly moving forward and attacking with their barbarian on their turn. Another one of the players didn't ready any spells and so could only cast the same one spell they did know over and over. They continued with the plot and found the person they were looking for, and it was supposed to be this big reunion. They responded sorta alright to it, better than the other events so far, but after that, we went into more combat. I had a displacer beast also join the fight and cause some chaos, but I had it run away because thats what it would do once it realized it was outnumbered. The vibes were just sorta, "yay. We did it." It wasn't the usual experience and it seems like even with these awesome ideas and fights Noone seems as into it as they used to be.

TLDR: Everyone seems to be out of it, especially the barbarian player. I should probably talk to them, right? But what do I say? How do I get the game to be fun again like it used to be? Is it even my fault? Maybe I should just throw more friendly npcs at them?