Cannot connect my postgresql db to my netcore project

I want to use my postgresql db from digital ocean in my webpage. Before i create this db, i have a free one for test and is working fine, but this new its not working. I can connect from pgadmin to the db.

My web project is a net core 2.1.

My connection strings

• From my test db (working):

  "Server=my-server;Port=5432;Database=mydb;                  
  User Id=myuser;Password=mypsw;");```
  
  

• From digital ocean db (not working):

  "Server=myserver;Port=25060;Database=defaultdb;
  User Id=doadmin;Password=mypsw;SslMode=Require");```
  
  

This is the error message: “The remote certificate is invalid according to the validation procedure.”

My web its certificated with Let’s Encrypt, certbot.

Can you help me?