Please help. I cant log in fgo

I have had this problem since last week. Every time I play the game using wifi, the loading screen with fou running just keep going on forever and then it days " connection error please try again ......" . However, when I play using mobile data, it works just fine. The same problem occurs to my Bangdream game too. Please help me if you can. I dont want to miss the Halloween and Christmas event.
Edit: Thanks guy, I tried resetting my network and the game is fine again.