Internet says it’s connected but won’t work

The internet connects and work for maybe 30 seconds but the the connection drops off and doesn’t work. I’ve gotten all my connections replaced and don’t think it’s a physical issue. I’ve take all the devices off the router to see if it was overloaded and it still didn’t work. I don’t know what to do and whenever I use chrome it says error network changed which I don’t understand how it’s changing