The switch loose VLAN 1 IP in the very moment, you configure another VLAN's IP. So I connect to the switch using VLAN 1 IP (192.168.1.254 as default) on e.g. port 1, configured a new VLAN, assigned the new VLAN (e.g. 999) to a port (e.g. as untagged...

Thanks a lot for this trick!