Hello, a question similar to this has been asked before and solved here. This is the best answer that was given:
If you forgot your master password, you can still use the Serial Number that you have used to register as the master key. Important: Please note that this feature only works if you have kept the Master Key option enabled in Password Security settings. Locking software has been developed to provide the most comprehensive and robust defence against any data-theft threat. One of the key defence features the application provides is removing any backdoors to this protection, which includes maintain password lists.
Unfortunately, if you have forgotten your password, and if you have not been able to set the use of the Master Key in Password Security settings, YOU WILL NOT BE ABLE TO PERFORM MAJOR APPLICATION FUNCTIONS, like LOCK FILES, UNINSTALLING APPLICATION AND SETTING CONTROLS FROM THE PROGRAM SECURITY OPTIONS IN SETTINGS! (depending on user settings)
Please make sure that you remember your password at ALL times or keep it in a safe place.
Last, for further help, I suggest you contact the Anvi Folder Locker Editor.