Hoi - Devices are connected to all cables that are also switched on/active? Switch has power?
Apart from unplugging all Ethernet cables and plugging in the cable on port 7 on 1-6 and 8 (and see if they light up green or not) as a test: not much; if only port 7 lights up, all others do not: then the switch could be defective => enter the return via customer account => service...