NextDNS not working with my Wifi

I have two wifi connection SSID is "2nd Floor" and "3rd Floor". From yesterday, one on them (2nd Floor) can't connect to neither NextDNS private dns nor DNS-over-HTTP. But "3rd Floor" wifi is working naturally. Even, there is no problem with app. Why this happening? What's the solution? Or my ISP banned NextDNS?