|I took a different view on your post but clearly that was incorrect. Sorry about that.|
What is your gateway address and what is the static ip you are assigning?
there is no difference between a static ip than a dynamically supplied one.
that is as long as they are in the same subnet. A ip address or its assignment won't make a router fail. You can even get the router to assign each pc a particular ip address as if it were static but supplied by dhcp.
now if you assiged it the gateway address you would cause a ip conflict and both interfaces would be disabled.
I take your "although everyone can communicate with the network." to mean that all 4 pcs to still talk to each other but not get to the internet.
If this is the case this means the switch part is working but from that part on something is broken.
Next step is when the internet goes down but all the pcs can communicate, can you get to the routers web interface?
If you can look to see if you have a ip address on the wan interface. It would be either the router or the isp. No ip on the wan interface would point to the isp.
Other tests can be done if we get to this point to isolate the problem.
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