Check first if there is a known issue in yiour location. Try in 2 places
1) Try the “check service,”Area status webpage" (link at top right of this forum)
2) Then also try the “free & automated” Service Status number - 0800 561 0061 - which usually gives the most up to date info. and tells you of more local issues down to street cab/ postcode level.
I have he SH2 as well, but its always been in modem mode with my own router and wifi equipment. You could always try that option. Back in the day there were lots of posts regarding the SH2 having flaky wifi as it aged - so yours might have that disease
That Hub model is very old now and VM are keen to have them off the network. So call it in as a wifi fault for a Tech visit - the first thing the Tech will do is swap out that Hub for a newer Hub3/4/5 which ought to sort the wifi issue.
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.