'filename.xlsx' is locked for editing by 'another user'. Open 'Read-Only', or click 'Notify' — when nobody actually has the file open

What's actually wrong

This is a false lock, not corruption — your data is intact. When Excel opens a workbook it creates a hidden owner file (~$filename.xlsx) next to it; if Excel crashes or the network drops, that marker gets left behind and every later open sees a ghost 'another user'. Background EXCEL.EXE processes, SharePoint's lock lease (which can take minutes to expire), and even Windows Explorer's preview pane can hold the same phantom lock. The file only needs the lock cleared — unless it then still refuses to open, which points to genuine damage.

Free fixes — try these first

1. Kill ghost Excel processes: Ctrl+Shift+Esc → Task Manager → Details tab → end every EXCEL.EXE, then reopen the file. This alone fixes the 'locked by myself' case most of the time.
2. Delete the orphaned lock file: in the file's folder, enable View → Hidden items, find ~$yourfile.xlsx, delete it, reopen. (It's safe — it only records who opened the file.)
3. On SharePoint/OneDrive, wait it out or check in: the server lease typically releases within ~10 minutes of a disconnect; also check the file isn't Checked Out (library → file → ⋮ → Check In), and ask the named user to close it — the name shown is sometimes stale.
4. Copy the file to a new name and work in the copy if you're blocked right now — the lock is on the name/handle, not the content.
5. Stop Explorer locking it: turn off the Preview Pane (View → Preview pane) — Explorer previews are a documented source of 'file in use' on shares.

If the free fixes fail

If clearing every lock still leaves the file refusing to open, or it now opens with corruption errors, the problem was never the lock — the file was damaged (often by whatever crash created the orphan lock). Our analyzer distinguishes an intact-but-mislabeled or intact-but-locked file from real structural damage in seconds and shows exactly what's recoverable if it is damaged.