the light layer settings won't let me choose the latest version

So I have updated to v27.10 on my Windows machine and was excited to try this new layer functions, as of course the blacks slider for instance is really useful. For a few days, I was able to use it… but now when I open ps, the Light layer defaults to the Legacy (before 2026) version and I cannot select the latest (recommended) version because it is greyed out! I’m not sure what changed. I can’t find anything in settings about it, but these menus are also a maze, so I’m not above asking for directions.