Guild Wars 2

I’m currently playing on the Server BlackGate and i have few friends who are from a euro server called UnderWorld and we tried to joining ascalonian catacombs and when we tried to enter it would give me the option to join them but when i clicked it gave me a code error and to check my connection. if this can’t be done bececause i’m on a us server and them on a euro one why would it even give us the option to join them there?
Also i cant see them in overflow of any map but i can see their dots on the maps that we’re on that’s overflow so that’s an small problem aswell

for a while now i’ve noticed i have no clue when my friends loggin and out of the game is there an option somewhere where the game tells me when a friend logs in the game since i don’t don’t check my friendlist a million times every min. if there isn’t i just might move this topic to the suggestion box unless someone beat me to the punch.