Unable to grant privileges with admin account

I’m running MariaDB version 10.4.8 on Amazon RDS. Once the server is up and running, I need to create some databases, users and grant privileges to those users.

Creating the databases and users works well, but when I try to grant privileges as follows:

GRANT ALL PRIVILEGES ON coredata.* to 'coredata'@'localhost';

I get the following error:

ERROR 1044 (42000) at line 13: Access denied for user 'dbadmin'@'%' to database 'coredata'

If I’m reading the error correctly, the user dbadmin doesn’t have the privilege to grant privileges, but dbadmin is the master user account.

I’ve read a number of other threads that suggested restarting the DB with the skip-grant-tables option, but as far as I can tell, there is no way for me to do that with RDS and it would make automating the process very challenging.

I assume there’s a simple solution I’m overlooking. Thank you.

Update: I’ve connected to the database using SSL, thinking this was part of the issue, but the issue persists. I can create and drop the database, I just can’t grant privileges to it. I can, however grant privileges to ‘test’ which was created by default.