What is shown under the source code schema is what Anvil has saved to the anvil.yaml file as a backup of your schema. What is shown under the default database schema is what it actually in the default database.
Generally when this shows up for me after I’ve just made a change to the default database schema the right thing to do is to click “The schema of Default Database is correct”. That updates the anvil.yaml file to match, and the message goes away for the moment.
There are times when the other answer is correct, but those are generally when you’re migrating changes from one database to another (e.g. from a development database to a production database).
Edit: the “Resolve” prompt is a shortcut to click “The schema of the source code is correct”, which is why it didn’t work for you. That undid the changes you’d just made to the database.