Didn't you check? This is fine, and the answers are 'Yes, I did' or 'No, I didn't.' Don't you check? This is also fine, and the answers are 'Yes, I do' or 'No, I don't.' Will not you check? This construction is grammatically correct, but very rarely used nowadays in standard English. It could be used in some circumstances, particularly to add emphasis if the speaker is angry or frustrated. Otherwise, it sounds archaic, or else regional/dialectal. In most cases, we would say: Won't you check? and the responses are 'Yes, I will' or 'No, I won't'.

First two are correct. Third one should be won't you check? Will and not together = won't. However the sentence itself seems like a rhetorical question. Hope that helps