I downloaded animations from the Unreal marketplace, and tried to retarget them to my mannequin. Everything looks fine in the Preview Editor, but after exporting animations, the animations are floating in the air.
I am currently using Unreal 5.7. Any advice on how to fix this? Thank you in advance!"
You probably forgot to select the root bone as one of the retarget ones.
You also want to retarget the IK - use just the hands and feet if the animation you retarget from doesn’t have actual IK bones (but it looks like it has them so use them).
Actually, because the character is up high the bone you must have forgotten is the pelvis.
Still, you should retarget the root as well just to make sure things match up with rotations being preserved and distances etc (for jumps).