Dunno if someone is having the same issue after the midnight's refresh- I just used my UW 3 costume and it seems like I can't attack anyone. The message says that the attack can't happen, try again later or choose another opponent. Hope that there is a fix to this, thanks in advance for any tips.
Whenever you have that type of error try to log in with a different browser. I hope you didn't have that problem again. Let me know if the problem persist.
This is normal and it happens whenever there is game data backup. It doesn't happen at the same time, so when you try to fight, the other player is being saved and can't take the fight, it will respond your challenge as soon as the backup is done.