When adding new page, "Allow Comments" checkbox does not show

When adding a new page on my two new sites I don’t have the “Discussion” option/menu for Allow Comments and Allow Pings.

On my old site, I still have this option (same version of wordpress, same template.)

I cannot figure out why this “Discussion” menu is missing on the new sites or how to add it in.

I also tried switching back to the Twenty Ten theme but it still doesn’t show. There must be a simple solution but after 3 hours I can’t figure it out…

Please help.