@Dannyz. I'm having the same issue. Main network pool is 10.0.0.0/24, first vlan is 10.0.1.0/24, and second vlan is 10.0.2.0/24. I have ACL rules setup blocking both vLANs from communicating with each other. However, I want to make an exception rule for the first vlan to be able to communicate with only a couple of devices on the second vlan and I want those couple of devices on static IPs. Problem is, Omada has the exact big you outline where it won't allow you to assign static IPs for clients in vLANs.

  @JoePalmer 

Try to retyp the ip address completely, it looks like the pre-typed address has a space in it or something else.

when i typed the address myself instead of using the pre-typed address it worked.

hopefully this will work for you aswell.

  @Fae 

I think there is a bug in the preconfigured address when selecting a VLAN when i only change the last digits it will not accept the change (ip address) when i retype the whole address myself it will accept the new address.

  @Dannyz. Unfortunately didn't work for me. Doesn't matter if it's preconfigured address or manually typed out. It only wants to accept addresses within the main LAN's pool. Not either of the vLANs'.

  @Fae I got it working. Instead of of doing anything on the switch, I setup the vLAN forwarding in the devices, which it supports. So the vLAn traffic is set to tagged on the switch, tagged in the master unit, and untagged on the slave unit's Ethernet port. Worked like a charm and then I set static IPs in the master and slave units.