Click on My Activity at the top of the page; your offers will display. Pick the one you have not been credited for by clicking on the "Missing Reward" button and a support ticket will be made for you,
We do not have the information on the offer you did.
We do not have the confirmation from their advertiser that the offer was completed properly.
We host these services for you to earn, we have no control over them.
They need at least 30 days to investigate what happened and to reward you.