Hi, @Cian Senior
To help narrow this down:
- When the different account appears, does the window mention Windows Hello, a PIN, or “Making sure it’s you”?
- Does that unknown account appear under Settings > Accounts > Email & accounts, especially under “Accounts used by other apps”?
- Are you signing in through the Minecraft Launcher, Xbox app, or Microsoft Store?
In the meantime, sign out of the Minecraft Launcher, Xbox app, and Microsoft Store, then restart the PC. Sign back into all three using the same Microsoft account that owns Minecraft.
Also, open https://account.microsoft.com in a private/incognito browser window and check whether you can sign in normally with the correct Minecraft account. This will help determine whether the problem is with the account itself or a cached account on the PC.
If the wrong account still appears, please let me know exactly where it appears in the sign-in process. A screenshot would also help, but please hide any personal information.
Click "Add comment" to let me know.
Thanks!