Devices not connecting to fortigate via a switch

Hiya

I've got a Fortigate 50e, acting strangely.

When my computer is directly plugged into the FortiGate, it shows as connected and can access resources that are also directly plugged in and the internet. However, when plugged in via a switch, such as an allied telesis or HP, it does show as unconnected and I'm unable to ping the fortigate or anything which requires data to go via the fortigate such as the internet or located on other interfaces.

I'm using mostly factory default settings.

Is anyone able to give me some pointers as to what's happening and how to solve this?

I never had this problem with my older 40c