How to check the DB Owner access for SQL Database?
* Open Database server.
* Login to SQL Manager.
* From left panel expand Securities -> Logins.
* Right Click the Sharepoint admin user or user which is showing access denied error
* Right click on Properties.
* On properties window, from left panel go to User Mapping.
* Select the Database with error and give dbowner rights see screenshot attached
* Click Ok.
* Test the scenario