So I haven't been able to send messages to most of my friends lately. Every time I do I get that error message that there is no player with that name. They can send me messages, I just can't send them messages. I think I figured out why possibly.
When I started playing ESOTU on Tuesday I chose the daggerfall covenant. After a couple days I noticed most of my friends were playing on the aldmeri dominion. I decided to make a new character in that alliance and that's when I noticed I couldn't send messages.
Now one of my friends just got ESOTU and he chose daggerfall covenant like I did. For whatever reason I can send him messages, but noody else on my friends list. It seems as though when I created my first account it linked all my messages to daggerfall covenant and now I am ONLY able to send messages to players in the daggerfall covenant.
I am in the aldmeri dominion right now and unable to send messages to anyone else in that alliance on my friends list. Only reason I can think I would get that message is if the game thinks I'm in an alliance I'm actually not in, therefore almost nobody else would technically exist when it comes to sending messages.