Old iMac with broken internet

[don't do it]

Ok this is a weird problem I have never seen ,but I have an old iMac 10.3.9 and about 3 or 4 days ago it decided it didn't want to connect to the internet any more. We have not a clue as to why this happened. The iMac is connected to a airport via a ethernet cable (which works by the way we switched out cables and still the same problem.) The airport is connected to a router which of course is connected to the phone line. We have two wireless laptops connected to the airport so it still works but we don't know why the desktop won't.
Help Please...
Thanks

 

[max¥¥]

I had the same problem on a mac mini, I ended up reinstalling the os😡

 

[don't do it]

that was the only thing that helped?

 

[max¥¥]

there are probably different ways, but the only way i could find was to backup my data and reinstall the os