That means that MobileSheets is unable to open one of the configuration files and add it to the library backup file. Even if you uncheck the option to save the settings, a few configuration entries still need to be put into the backup file, and even that is failing. If you go to your tablet settings->Apps->MobileSheets->Permissions, can you verify that you've granted the storage permission, and if you are on an Android 11 or higher device, the "All Files Access" permission? If you've granted both of those, then the next thing to do is go to Settings->Other Settings->Reset Settings to Default in MobileSheets, which will reset all of the configuration files, annotation favorites, custom stamps, etc, and then try to create a backup file. Hopefully that will resolve whatever is causing the backup to fail on your device. Without having access to the device, I can't provide more information unfortunately. I will be adding more logging in the future so that users can send me information when things like this occur. If you don't mind installing a new build, I can send you a build that prints out more information about what is causing that error which may help us understand what is going on. Also, if you have not done so yet, please reboot your device to see if that changes anything.
Mike
Mike