Hi, welcome to Microsoft Q&A!
Thanks for reaching out, Annie. From your description, it seems like Minecraft is automatically signing in with your son's account and not giving you the option to switch users. I understand how frustrating it is, especially when the back button just loops you back to the same screen.
The first thing I suggest you do is to check the accounts from Windows, Microsoft Store (or Xbox if you use that version). Minecraft often uses their services in the background to sign you in, so if your son's account is signed in via the Xbox app or Windows Settings, it can override Minecraft.
- If you are using the XBox app > Open it > Click the profile icon > Sign out of your son account.
- If you're using the Microsoft Store version > Do the same thing to sign out of your son account.
- You can also check Windows Settings > Accounts > Email & accounts > Remove any unwanted Microsoft accounts linked to the PC.
- Restart your PC > Sign in with your Microsoft account before launching Minecraft.
In case that doesn't work, I also have some other deeper and more advanced solutions that you can try out to see if the situation improves.
- Clear Minecraft account cache:
- Press Win + R > type
%localappdata%\.minecraft
- Delete (or rename) a file/folder called launcher_profiles.json
- Press Win + R > type
- Reinstall Minecraft launcher (last resort)
- Open Settings > Apps > Installed Apps > uninstall Minecraft
- Download the latest launcher from minecraft.net
If you are still stuck, consider contacting Minecraft Support and explain the auto-login issue. If it’s a child account, you can also set some restrictions via Microsoft Family Safety. Let me know if you'd like help walking through any of the above steps. Thanks for your patience!
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Warm Regards,
Lychee-MSFT | Microsoft Q&A Support Specialist