Five WiFi bars but no internet in one room???

Hi,

I have been using an Airport Extreme in my house for years. It has worked for all of our computers (we have five Macbooks) without any problems. A few weeks ago, my son (intermittently of course - because that makes it harder to solve) loses internet access in his room. The thing is that - even though his room is furthest from the Airport - he still has five bars, but no internet. Sometimes it works great, and then all of a sudden he will lose the internet for hours. I bring my ipad and computer in the room - from just across the hall and I keep the five bars but lose the internet!

Any help here???

Thanks so much.

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