It's probably a problem with your router. Try to turn off and on again your router and if that doesn't work then use a pin to reset the router on factory settings. Note that if you reset your router on factory settings that the password and username will be reseted and all the connected device will disconnect from the wifi so you have to connect them once again.PS: A guy had the same problem and said that he contacted his ISP and the problem got solved but I think if you try everything that I told you that you won't have any problem. (https://cit.gg/index.php?topic=350001.0)
not working extreme