Move everything from around the couch out of the way, leaving the sofa exposed. Check underneath the couch, looking for anything that might block the reclining mechanism and remove it. Even a book or magazine can wrap around the mechanism, locking the recliner.
Spray the underside of the reclining footrest with spray lubricant, avoiding the fabric. Thoroughly coat all metal areas with a thin layer of the spray and let sit for a few minutes. The spray loosens any stuck components and removes rust that might cause sticking.
Turn the couch over on its side and look at the inside of the couch. Spray the interior mechanisms with a thin layer of the spray lubricant. After the spray settles onto the metal for a few minutes, tip the couch flat. Try working the lever up and down.
Flip the couch back over and examine the underside around the reclining lever. The problem might relate to a buildup of paper or another item trapped around the lever. Remove anything surrounding the lever and try moving the footrest again.
Stand in front of the couch and push down firmly on the footrest, as you push down on the side lever. Keep exerting force on the footrest until it pops back into place. If the recliner still stays in a locked position, it indicates a problem with the lever mechanism.