Do you have the two expansion packs for Roller Coaster Tycoon 2 installed along with your base game? Our servers occasionally have scenery objects and rides that belong to them and thus playing OpenRCT2 with just the base RCT2 installed instantly disconnects you from any server using those expansions. 

If you do have the two expansion packs and still have this issue let me know if this issue persists, in the chatroom.