Launcher keeps asking me to enter a username

Clicking on play on official vanilla launcher was doing nothing for a while, and then I restarted the pc, logged out and in again on the launcher and now I am being asked to enter a username for Minecraft Java Edition - I have a username already, and when I put in my current username, it says that name is taken and to choose another one. I did try entering another one in the dialogue box that is demanding it, but it just says “failed to create profile”. I am not trying to create a new profile, just use the one that already exists. Please fix quickly, this has made the entire game totally unusable.