The bolt probably got uncocked. Hold the sleeve and raise the handle until it catches. Then swing the extractor to the right (same side as handle) and insert bolt into receiver with lug up. Turn clockwise and (simultaneously) snap extractor into slot. MUCH MUCH harder to describe than to do!

FWIW, true Model 1898 Carbines are pretty scarce. Most so-called "1898 Carbines" are actually shortened rifles. Serial number needs to be in the 112000 to 135000 range. Is your stock 30" long, or 32"?