They just say the address must be "bitcoin network" without explaining further.
So I am not even sure they know what they're doing.
Is upbit famous? Anyone actually tried?
You didn't mention the specific message but if that only shows when you paste the type of address you mentioned, then it's possible that they don't consider it as a valid address although I doubt it... because Upbit is actually a very known exchange, at least within the Korean community.