I'm hitting a weird dead end with your sprites. I was already able to make one last night that worked fine, but when I opened up your stuff this morning it keeps importing into GB Studio as 0 frames (Invisible). Not even close to sure what's happening. I've gone into the sprite editor and made sure it was 16x16 as well as went into aseprite and made sure the settings matched my functioning sprite.
Not sure if anyone will ever read this nor reply, but figured I'd write it anyways instead of beat my head against the wall for nothing.
Viewing post in GB Studio Character pack comments
So I've just tried importing a character into GB studio and it seems to be working fine on my side. I'm assuming that you imported a single character sheet into GB studio and not the png that includes all the characters?
If you are still having problems might I suggest joining the GB studio discord, there are a lot of people there that know more about the program than I do and I'm sure they will be able to help.