If you have an encountered with an error like this and playing outside of NA or Canada, you need VPN to play and have access this is the common error on JP server since the game is region block. Turn off both vpn and your game(forge stop it)... OpenVPN (Or any VPN for Canada and NA, also it might not work on all VPN app but try to reinstall until it let you bypass the error) again make it connected to NA or Canada 1st then open app. Second method is close both and restart your device open vpn and connected it to vpn 1st then open your game. Reroll here is easy personally I'll go for Fafnir since he's the only one that has self heal on the game, otherwise you can aim for Thor(She is the best for Chapter 2 boss since she has type advantage make it easier to clear it) or Apollo. If we follow the jp schedule first event would be Schwertleite she is a a burst dps too after that you can skip and save for limited units.