Hi,
Local gateway is always enabled on the standalone edition of KNM 5. What happens though is that it will run a network discovery, and all devices that it finds are put in a special group called "Discovery group". While devices are in this group, they will not be tested. To have them tested, you need to move them outside this group. For testing, or if you just don't know yet how to build your structure, you can move the devices right under "Local gateway".