Heyo, I just started to see this problem, I did also just update to a newer version of the launcher. Whenever I try to join a multiplayer server or realm minecraft states that I have an invalid session ID, in which I have to exit minecraft and log back into the launcher. Next, whenever I try to log into the minecraft.net website it loads, verifies a token, then it briefly says not logged in and kicks me back to the log in page.
I have no idea what's going on, though if anyone has some idea to help that'd be great. I'm launching minecraft through the latest update 1.15.2
Say something silly, Laugh 'til it hurts, Take a risk, Sing out loud, Rock the boat, Shake things up, Flirt with disaster, Buy something frivolous, Color outside the lines, Cause a scene, Order dessert, Make waves, Get carried away, Have a great day!