If nothing works, then login to your Harmony Gateway using an FTP client, for e.g. filezilla.
Host: IP address of Harmony Gateway
port: default FTP port, don’t change
once you login, you will see a few files, like nodes.bin, config.inp etc..
Open the config.inp file. Replace the password with 09cbef6f2f30e9bf9a202c53142295478786d5f3
So make sure the password looks like below:
password=09cbef6f2f30e9bf9a202c53142295478786d5f3 # Encrypted pwd for authentication purposes
Close and save the config.inp file. Now reboot your harmony gateway and you should be able to log in to the App with the password Smartenit. If the App continues to give you Authentication Error, then that might be a bug in the WebApp, please let me know how it goes.