I replaced a breaker box in my garage with a larger one. After reattaching all wiring to the new breakers everything worked perfect. The box holds 12 breakers but only six have the correct voltage and I want to add more breakers which is the reason for the larger box.

Looking at the box... There are 12 slots.. 2 side by side 6 down, every other set of 2 only has 60 amps. Where did I go wrong?

Thanks for any help

Need a picture of the interior of the panel to see how you wired it.

The possibilities are endless.

Verify the neutral is on neutral bar, and Each Hot is on the correct lug to supply power to each Buss. Wonder if you have a hot and neutral reversed.
Measure voltage between the ground and neutral. And all combinations between the 2 hots and neutral.