We must supply the omitted verb ediōxa (pursued) from Rom 9:31. That explains the rest.
They stumbled at the stone of stumbling (prosekopsan tōi lithōi tou proskommatos). The quotation is from Isa 8:14. Proskoptō means to cut (koptō) against (pros) as in Mat 4:6; Joh 11:9. The Jews found Christ a skandalon (1Co 1:23).