Removable plates are orthodontic appliances that clip onto the teeth with small wires and have a plastic part on the inside. Their effect is mainly orthopaedic – that is, they act on the jaws, encouraging them to widen or to grow in a way that corrects a bite problem. Of course, the wire components can also move teeth, but they rely mainly on tipping them in a particular direction. So if a plate is worn by a child who needs their jaw growth stimulating and whose permanent teeth are still coming through, the plate will guide these teeth into their correct position while it corrects the bite. If a plate is fitted for an adult, all the movements of the teeth that have already come through will be tipping movements. Such movements are not stable, and the teeth immediately want to go back.
This answer is for general information. Your own case needs an examination by an orthodontist.