why can't i open emails with attachments on my ipad

What happens when you try? More info would be helpful. In any case, the first thing to try is a reset, cures 99% of glitches. Hold down the home button along with the power button until you see the Apple, then let go.

You can't open the attachment or the entire email?

If the attachment is a video, it may not open if it requires flashplayer.

The email with attachment shows on laptop, but never comes up on same account on ipad

The entire email does not show up in inbox if there is an attachment.

Had a similar problem, I just "re-booted" my iPad. That appeared to have sorted the problem.