UPDATE: There may be a problem with the 4.0.6 release that I need to investigate further - It is possible that after the initial discovery the plugin may lose contact with the LIFX devices.
If you have downloaded and installed 4.0.6, It is probably best to revert to 4.0.5 else stick with 4.0.5
In the meanwhile I have set the 4.0.6 as a Pre-release on Github.