Sometimes, the terminal won’t respond to your fully charged key. You can come back later, next day, whenever, and it will work.
I suspect what is happening is some people are using a key on it during the FE event, knowing full well there are a lot of people that enjoy doing that immediately after, and knowing that it will ‘lock out’ the terminal for a period of time, so we all get griefed.
If there is a timeout on that terminal, remove it. It makes no sense. If you have a key, it should open, and you get to fight the boss.