Sign in to wifi-network

So I'm currently connected to my wifi but it keeps asking me to sign in even though it's connected. Wifi keeps showing "!" Symbol on it and it's pretty much annoying me. I've already restarted the router as well as forgetting the wifi password and signing in again. It's been working perfectly fine until now and all devices connected to it show the same message, so it's obviously not a problem with my phone. Any suggestions on how to fix it?