ATTRIBUTES (flags, labels and ratings) not visible on the first roll of Lr.

I don't remember exactly which version of Lr Classic for MacOs I'm experiencing the following issue:
- Launch Lr
- Import RAW photos from an SD card.
- Lr converts the photos to DNG.
- I start evaluating DNG photos with colored Flags and Labels, but these attributes aren't visible in the grid view (for example, rejected photos don't appear shaded and with a black flag).
- I quit Lr and relaunch it.
- Now in the grid view I see all the previously set attributes, and if I assign new ones, they are perfectly visible.