The bolt hold-open is a small push pin (operating slide stop pin item 12 on the NRA Firearms Assembly Rifles and Shotguns Manual) on the top of the operating slide at the base of the finger hook. It engages a recess in the receiver at the rear of the operating slide's travel. Look on the right hand side of the receiver near the end of the operating slide's travel. The recess may have some debris built up in it, if so just clean it out with a non-marring tool (plastic, nylon etc) then move the operating slide to its rearmost travel and press down on the hold-open pin. If this does not solve the problem then the hold-open pin itself may have been damaged and need repair or replacement, recommend gunsmith's attention for this.
charliemeyer-Great read. I copied it for a good reference. I cleaned the complete carbine including spending time on the push pin and got it working. Will look into the type 3 pin senario. Much thanks for the replys.