Luminosity Masks

PS has just updated to 27.11.0 and I’m no longer able to use the luminosity masks action that I had been using successfully up to now. It makes an attempt to create the masks but after several error messages, it will only create a selection of the total that it normally would.

I work in Lab colour mode but it’s also affected in RGB also.

I just need a simple action that can do as I need, I don’t want a separate plug-in. A bit baffled as to why this is happening.

Any help would be greatly appreciated.