On my network, I have two VLANs: VLAN1 and VLAN10. I started with 2 acces points TL-WA1201, and in those, I can create the two VLANs. 

Both vlans work well.

I recently added an eap225-outdoor and I just wanted to copy these settings.

However, if I do, on vlan1, devices do not get an ip-adress. Devices on vlan10 work fine.
On this forum, some people people had the same remark, and the solution seems to be to disable vlan1, so to have an ssid without vlan. 

I tested this, and it indeed allows devices to get an ip adress.

Why do both systems from the same supplier behave differently?

What is technically the difference between no vlan (disabled) and vlan 1?