It just says that Xenoarchaeology is required. I think that's one of the few places where the text doesn’t fit at the default text size, and where it also correctly uses uses ellipsis to show that. You just have to wait until your xenoarchaeology units decypher the alien writing; it’s based on a random chance every construction cycle, so it’s impossible to say exactly how long it will take. More units will speed up the process though.
