I think you should take a closer look to this article https://www.router-reset.com/when-and-how-turn-wifi to find out how to get inside your router, this could be a connection issue, but mostly this is because your router's cache is full. The only one way to fix this issue is to perform a restart. You can do that in two different ways, you can find your router and press a button on the rear, hold it for 10 seconds and that will fully restart your router, or you can find a better way how to do that reading the article and you will find out how to enter your administrator panel and perform a reset of your router. More than that you will find there some useful tips that will help you to improve your router a little bit
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