By stopped working, do you mean.... dead to the world - or no connectivity but flashing lights everywhere?
The Tech will usually just swap the Hub from their stock and see if that fixes it. If not they will then investigate the cabling/connections etc.
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John
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I do not work for VM. My services: HD TV on VIP (+ Sky Sports & Movies & BT sport), x3 V6 boxes (1 wired, 1 WiFi, 1 on PA) Hub5 in modem mode with Apple Airport Extreme Router +2 Airport Express's. On 250Mbps, Talk Anytime Phone, x2 Mobile SIM only iPhones.