The likely cause is that the file you are restoring does not contain the data you think it does.
Possibly you have multiple backup files and are restoring the wrong one or you have overwritten your backup file with an empty wallet by accidentally backing up instead of restoring.
Restoring a database only replaces your current data file with the backup file. It does not change the contents of either file and can never display data it does not contain.
If you store your data in Dropbox, you can recover earlier versions of the file using the Dropbox web site. https://www.dropbox.com/en/help/11
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