Which accounts or services are still showing unfamiliar activity, and do their security records show successful sign-ins after your password changes, or unsuccessful attempts? Also, did you wipe the computer using Windows’ “Reset this PC” option or reinstall Windows from a USB drive, and were your passwords changed before or afterward? Please share the wording of one recent alert, or a screenshot with personal information hidden to better identify what is happening.
One additional step is to sign out existing sessions for the affected accounts, starting with your main email account, using a device you trust. For a personal Microsoft account, follow:
Microsoft says this can take up to 24 hours and excludes Xbox consoles. While reviewing that account’s security settings, check whether its recovery email addresses, phone numbers, and verification methods all belong to you. Unfamiliar entries would help identify another way someone might retain access.