Aviary Bottom Problem

Can anyone help me out with my budgie? He’s a little dude, still young I think, but he won’t fly. Like, at all. Just kinda walks around the bottom of the aviary like a tiny penguin or something. I’ve tried putting him up on perches a few times, but he always ends up back on the floor eventually.

He’s eating okay though, so that’s good. Also, I noticed his tail feathers aren’t fully grown in yet—could that be why he’s not flying? Anyone know what’s up with this? Like, is this normal, or should I be worried? Thanks!
I have included a short video, maybe someone can spot something I have missed. He’s a lovely bird and I truly hope this is a young bird thing.

