 So, you're importing rigs to Unreal and it's telling you the following bones are missing from your bind pose. Not a problem. This error means that your character's weight paint data is missing information about bones that Unreal 5's mannequin needs to recognize it as the same skeleton. So to solve this, look at the names of all the bones that it says you're missing. Then go find and shift click select all those bones. Then shift click the body last and under skin, edit influence, add influence. You're done. Now that you've exported now, the skeleton should have no more errors. Hope that helps and as always, hope you have a fantastic day and I'll see you around.