Hi Nirav,
Just a silly check - but hit refresh in the bottom right and see if they're still pending. They shouldn't be after 24 hours. If they're still there you could contact support, it's possible that something has gotten stuck and needs to be pushed through.
Usually pending means Marketo is processing the campaign and the emails are ready to go out, but have not been sent just quite yet. Or, pending could also imply that the emails have soft bounced, and Marketo will continue to try to send them a few times before recording them as an official bounce.