Internet access not working

Question

Hi, 
 Ive run into two main issues while setting up my Sophos UTM. Any help would be greatly appreciated. 
 1. No internet access 
 2. Inter-vlan routing doesnt work. 
 I am running Sophos from my QNAP with a Cisco SG300 L3 switch. DHCP is provided by Sophos and is working great. From every vlan on the switch i can ping the default GW (172.20.99.1) and access the management page of Sophos. 
 My internet PPPoE is set to the External WAN interface and connects to my provider successfully. From Sophos i can ping out with no issues. From my switch using my transit vian 99, i can ping out with no issues. But from a pc on vlan 99 im unable to ping out. Also if i connect to the switch under any other vlan im unable to ping out from the switch or the pc on that vlan. I have also tried (any - any - any) firewall rules but this doesnt make any difference. I have masquerading and firewall rules to get out to the WAN and allow access between vlans. 
 My switch is using port 28 as a trunk port with all vlans tagged bah the native vlan 99. Each vlan has a default ip address set to 172.20.x.1. The switch has a 0.0.0.0 route to Sophos on 172.20.99.1. 
 Im not sure if there is something im missing while configuring Sophos or if ive missed something on the switch.

DavidBonavita · Accepted Answer

Solved. 
 Turns out I didnt do anything wrong. After I brought the DHCP and routing to the L3 switch it was still not working. I then realised the work laptop i was using still had the firewall turned on which was causing ICMP and internet connectivity to be blocked. I used a spare laptop i had lying around and everything worked straight away. 
 I do think there should be better documentation from Sophos which shows a complete setup with pictures of Vlan tagging, DHCP, DNS & internet configuration. At the moment its only individual sections of text. I have seen a lot of other people having similar issues to me while setting up the UTM. Pictures are worth a thousand words.