Netgear GS724TPv2 Issue pinging devices? VLAN concern?

So the past week and a half I was at this job site configuring one of these for 2 separate VLANs. After reading some of the documentation and what I'm familiar with in terms of what will manage the VLAN and trunking and so forth I still couldn't understand how this piece of equipment worked. The closest I've thing that came to a suitable understanding was that if you treat the ports similar to Cisco switching it'll be more understandable then "Tagging" and "Untagging" the ports. The description in Netgear help manual reads off as so;

U, Untagged, means traffic is not tagged with the VLAN ID on Egress, when it exits the switch, to the next upstream or downstream device. T, for Tagged, means traffic is Tagged with that VLAN ID, and it will be preserved as it Egresses the switch. Blank, means that there is no participation for that VLAN, and that it will not Ingress, enter the switch, or Egress the switch at all, on that VLAN, from that port.

So at first I was a bit confused but as I said it was later and better explained to read it like "Trunking [T]" and "Access [U]".

Anyway, to get to the point I set up 2 VLANs from a Fortigate 60D. I've been dealing with Fortinet equipment for a couple years now and thought I had it all set up. On the Netgear switch I had 5 ports dedicated to a different VLAN for this AV companies equipment (10.1.1.0/24) on the Netgear I established ports 14/16/18/20/22 as the VLAN20 and on the web interface they were filled in as [U] ports while port 23 was tagged [T] to "Trunk" the VLAN over. After all was said and done I was able to ping my phone, my laptop, a couple of other devices both hardwired and wireless under that subnet. When it came to the AV equipment I couldnt ping their devices. They have this Crestron setup with 3 pieces of equipment that required static IPs. I assisted and setting that up with him and even ran some network testing, still no way of pinging those devices. Tested the ports in the room if they were getting internet and it resolved both a DHCP IP and using a Static for my laptop. Both had access to the internet and you could ping my laptop both through the wifi and wired connections. Checked the DHCP of the firewall, the VLAN was handling it, and saw his devices with their mac address come up but nothing still on the pinging efforts. Eventually I just took his connections to the switch and put it on the native VLAN and all of a sudden everything started connecting and pinging.

Just wondering if I may have missed something or wasn't aware of how these are set up? I haven't had an issue with other Cisco and FortiSwitch products but they were pretty straight forward in their set up. For the Netgear I'm not to familiar with but I figured I could apply the same idea as what I know with the previous products mentioned.