To defray misunderstandings, here’s a friendly, but unofficial reminder as to what red dots mean and how they work:
Short version: the red dots indicate whether the time slider (including in “live” mode) is set to a valid time within the mission itself. That’s it - everything else is derived from that. So for example, if the slider is set to live and you have a red dot, then, yes, it means the mission is valid now, indeed “live,” but this is a specific use-case - it goes deeper.
If there is no red dot for the desired mission, move the time slider around and watch one show up when you’ve selected a valid time in accordance with the mission parameters. Note that some mission types have looser valid times than others. The advanced map layers and weather depiction changes with the slider, using historical weather at the selected time within the past 24h. Use the presence of the red dot in conjunction with the slider and those layers and to preview the historical weather the sim will give you when you start the flight (or live if the slider is set to “live”).
Note that this is not valid when bugs or server issues show up.