Does this happen as soon as you click the icon, or just after you pick your character?
As soon as you click your icon:
If this happens as soon as you click your icon, then I would suggest redownloading, because it may be something you downloaded incorrectly, otherwise it's a common problem. You may even want to take out any recent mods /objects/markings/maps you have downloaded recently, this could help too.
As soon as I pick my character:
This would happen because the servers are too full, especially when entering fluorite. They lowered the servers from 300 to 160 the other day, which causes a lower number of users to be in a map at once. Just keep trying to get into that map, or go into a less crowded map. Yes, this is an inconvenience and I'm sorry for that dear.
Hope this helped, if you have any further questions, just ask ^^