Hinged panel or vertically?
Is a hinged seized up or is it that the table will not go up and down to make the setee a berth?If a hinge, consider the possibility that varnish or other woodcovering/cleaning liquid was used, ran onto the hinge, then allowed to dry. On a long piano hinge like on a table leaf, this could be sufficient enough to prevent motion. Just dab lightly with your favorite solvent and let sit while ensuring no drips run across the varnished table top. This happened to me on cabinet doors; every hinge squealed so badly it was nearly deafening to open any door. When removed from the door, I could not manually move the hinge at all. Soaking all the aluminum hinges in a tub of varnish remover overnight removed roughly 90% of varnish and now all hinges operate with no noise at all.