Yoast overall score is not updated, always Unknown and gray.

I had this problem as well and yoast_seo_update_8203 should've taken care of that and created a settings file.
Do you have a yoast_seo.settings.yml file with the contents below?

score_rules:
  0: 'Not available'
  8: Good
  1: Bad
  5: Okay

That update was somehow missing.
Now it works for some cases. But not for every content type.
But I don't know yet why some content types have scores and some don't.