About the db-owner Permission in MS-SQL

[CornerLeafe]

Hello friends, I have a VDS server. I have installed Plesk Panel on this server. I have created a database through Plesk and established a connection with Management Studio. My issue is that when I connect through Management Studio, I cannot access the diagram sections of my database. Similarly, I am unable to write queries. The error I am receiving is as follows: [Link to the error image]. No matter what I do, I couldn't grant myself the db-owner privileges. There are no issues locally as I mentioned. However, when it comes to the host, the problems persist. Could you please help me with how to grant this privilege?