Was it working before? Did you change anything about your setup? (For example, openutau folder location, or updating the version, or switching from stable to beta version)
I remember this, we had a bug from an old update that messed up the data in prefs.json. After deleting the file a new clean file will be created, and you can edit your preferences again.
Was it working before? Did you change anything about your setup? (For example, openutau folder location, or updating the version, or switching from stable to beta version)