In the ones that work the way you want, you have placeholder text formatted as such. In the ones that are not working, you have placeholder text formatted as grey. The first is the default; it is the way content controls are inserted.
Click in the first one that works, Press
Ctrl+Shift+C (Copy Formatting). Then click in each of the ones that are not working and press
Ctrl+Shift+V (Paste Formatting) to paste the formatting. I suspect you typed something in one of the original controls and then typed in the placeholder text and formtted it as grey. To change the placeholder text, you want to be in design mode.
Here are some links that may help with
Content Controls.