Welcome to the Forum Cknpro
You may have the wrong Mags for your CZ if they are not being held by the Mag Release
OR, you have a bad Mag Release
If the Followers don't rise all the way to the top, the Mag Springs may be bad
If they do come to full height, try the Mags in the Frame without the Upper mounted but with the Slide Stop inserted
See if the Mag's Follower lifts the Slide Stop
If not, you my have a Slide Stop issues
Without seeing the Mags, it's hard to give other ideas