Hi. I have the same problem. I made a thread weeks ago about this issue but never got any replies.
I migrated my EU patcher weeks ago and I get the server:undefined message, so I've been playing on US servers since I hadn't migrated to the new US patcher and the old one works fine. Now it has forced the migration to the new patcher and I can't play at all on either US or EU.
I'm very sure it's due to my internet connection, I'm currently at university and I know they block various things. I always get a crappy NAT3 connection with consoles, whatever that is.
In short, I am able to play using the old launcher AND the new launcher at my home address, but under the restraints of my university internet connection only the old launcher works.
My current internet also has never let me download/install the game, that's why I couldn't just re-download the old patcher and play on the EU servers again.
I live in the UK.