I have a problem with opening a database created before
Manager data is stored in SQLite database. However it appears the file you are attempting to open is not a SQLite database.
What edition of Manager - server, cloud, desktop?
What version?
What Operating System?
What version did you use before?
Where did they business file come from?
Have you a backup?
You need to provide a lot more information if you want any real help
@Bahruz_Gasimov See this post and the linked post Manager 20.9.89 conversion error - #6 by Patch