Hey there, I am having a problem with my

[ashen hamlet]

You're uploading the model to mixamo and having it's auto rigging system build a rig for it, is that right?

Could be that the fingers are too close together and it can't differentiate them or maybe it's just a limitation with the auto rigging system as a whole

Learning to use something like rigify with blender is more robust but also more complicated with a bit of a learning curve, CGDive has some pretty good vids on it tho