Corrupted Session
Starting in Notepad++ v8.6.5, it will store session.xml.inCaseOfCorruption.bak next to session.xml, and will automatically use that if session.xml is corrupted.
However, if you ever find that you open Notepad++ (especially after an update or a system crash) and find that the files opened weren’t in the same state as when you let them, you can try this procedure:
Exit Notepad++
Windows Explorer, go to %AppData%\Notepad++ (or in your appropriate config-file location if you aren’t using AppData for config)
Rename session.xml to session.xml--keep
Copy session.xml.inCaseOfCorruption.bak to session.xml
Run Notepad++
→ If it’s now showing the right copy of your files, great!
If not, exit Notepad++, delete session.xml, and rename session.xml--keep back to session.xml .