I've field stripped this weapon many times in the past with no issues. This time, after field stripping, cleaning and re-assembly, I've noticed I can't get the slide to move forward again. I can however, slide it all the way back. I SUSPECT the guide rod spring and rod slipped off the piece with small radial cut. (Sorry, not sure what this piece is called.) Any tips would be greatly appreciated. Thanks.

Assuming you mean the slide is all the way rearward, and you have reassembled, is there any possibility that the slide stop is unintentionally in the UP position locking the slide back, preventing it from moving forward?

Negative. The slide stop pin is removed. I can re-phrase this and say I'm field stripping it... I pulled the slide back, removed the slide stop pin. At this point I should be able to move the slide all the way forward and remove it from the rail, exposing the guide rod /spring and barrel. It will not move forward far enough to remove it from the rail. hope this is communicated clearly enough. thanks!