It seems the dummy rounds were too large for the chamber and got jammed in there snug.
Were it mine, I'd get a dowel that fits down the barrel. I would then tap it against something solid or the floor while trying to retract the slide at the same time. Since it's a dummy round there's no safety issue and you can tap pretty hard.
Anything will work in place of the dowel but I always go with something soft so as not to damage the barrel lands etc.
If you have a vise you can clamp the dowel in the vise and run the gun into the dowel again while pulling on the slide.
In Memory of Paul "Dietrich" Stines.
Dad: Say something nice to your cousin Shirley
Dietrich: For a fat girl you sure don't sweat much.
Cue sound of Head slap.
RIP Muggsy & TMan
"If you are a warrior legally authorized to carry a weapon and you step outside without that weapon, then you become a sheep, pretending that JOCKO will not come today."