The instance you’re on has a 100 kB limit for images. The last I read at least.

lemm.ee has temporarily disabled all image uploads actually, due to the csam spam (see the post on !meta@lemm.ee)

/0 has recently released his ai anti-csam filter though, so hopefully they should be back soon

I'm using liftoff on lemmy.world too and don't seem to have issues.

Maybe you could try reinstalling the app or use a browser to test things out.

seems it has something to do with image size, try downsizing your image, that worked for me.