The following are the possible causes of this error:
1. This error usually occurs when a database file or folder that contains the file does not have IUSR Windows NT permission. i.e., you have uploaded a database file other than the site's db folder.
Please move or upload your database file into the db folder.
2. Another process or user has the Access database open.
3. Use absolute path in database connection string such as C:\domains\yourdomain\db\database-file-name.