Long time ago (few months in fact), EU server started to bug itself, when too many people try to join it same time.
In most cases, it works like this:
People wait on EU_3 to start strategus battle, then all get kicked, and try to join EU_3 same time. Server let first 50-60 people in, but then for some reason stops responding for everyone else who try to join it (whole machine, not just EU_3 - so EU_1, EU_2, EU_3 etc). It looks like some kind of network attack protection or maybe something completely different, hard to guess.
After some time it normally unbugs itself, most of the time after 5-10 minutes (this might suggest network attack protection). But today it didn't fix itself yet, so no one can join official EU servers atm. Maybe the whole machine need to be restarted this time to fix this problem.