Custom field data entries not saving

Hello MP3 Tag,
I just bought the software from the Apple App Store for macOS.
I ran into an issue right away.
I made custom fields and none of my entries are being save when I hit "save".
I'm able to change the data in the standard fields like Title, Artist, and Album.
I added some custom fields that are specific to my original music licensing needs like Publisher, Contact Info, and Copyright. However, when I enter the data in those fields, as soon as I hit save, everything disappears from that field.
Pleas help!

Hi and welcome!

Thanks for your message and for your support!

Have you added the custom fields to the Tag Panel on the left via Preferences → Tag Panel? An example configuration for the Publisher field would have PUBLISHER as field and look like:

If you added these fields as new columns to the File List via via Preferences → File List, an example configuration would have %publisher% or $metasep(publisher,\\) as Value and %publisher% as field and would look like:

Can you double-check your configuration? And if it doesn't work, please show some details so we can investigate together.