Mutant keys not usable anywhere

Since day 1 of the mutant event I haven't been able to use my mutant keys on the mutant briefcases.. the mutant briefcases don't show up as an option at all in my loot section, and when I click on the keys in my inventory they display a message saying currently unavailable. I've been collecting these keys and would love to be able to actually use them, so any help with this would be greatly appreciated!