It's possible that the da_admin user doesn't have the required privileges to write to the mysql.user table. Check /home/mysql/* and make sure it's all owned by mysql:mysql, but the issue might be a permission issue inside the database table itself.
If you don't have anything in the database yet, I would recommend you just reinstall mysql using our script:
./mysql.sh rootpass da_admin adminpass
and chose "yes" ('y') when it asks to delete the directory.