There isn’t a deadline for an election result to be challenqed, if I’m understandinq correctly.
There is a deadline to challenge it in state court, in every state. The MS Supreme Court held that McDaniel blew that deadline. Ultimately, though, the Constitution says that the Senate is the final judge of all election challenges to the elections of its members, so in theory McDaniel could challenge Cochran there.
BTW, couldn't you replace your old keyboard to get a working "G" key again?