Last Updated: November 25, 2017
When opening an Access runtime application (.accde file) saved with Access version 1710 (Build 8625.2017 or greater) in an earlier version of Access, you will receive the following error message, and the application will not open, "The database is in an unrecognized format."
This issue is now fixed in version 1710 (Build 8625.2132). To get the update immediately, open any Office 2016 app and choose File > Account > Update Options > Update Now.
Once you've updated to the latest version, you can reopen the .accdb file and then click File > Save As > Make ACCDE to recreate the .accde file in a format that can be used by version 1709 and earlier.