Ethernet switch (GS308 Unmanaged switch) not working

Recently purchased a GS308 8 port unmanaged switch. Connected it to my Virgin Media Hub 3 to increase the number of Ethernet Ethernet outputs. Unfortunately the switch only works intermittently. I connect Ethernet cable from switch to laptop and more often than not it connects. Unfortunately after a short period of time it drops out. I have checked the input to the switch and it is fine (lights all indicator lights on my tester - 1 to 8). However, when I test the switch outputs my tester only lights up the indicators 1, 2, 3,  , 5, 6, 7, 8 with no light on 4. All switch outputs give the same test reading. All cables are new with factory made connections so don't think my patch links are the issue..

Please advise.

Thanks.

Mark D