Databse schema could not be retrieved for this connection

SQL Server Administration
1

I am running my visual studio 2017 project in the server.sql used is 2017 version.The project is running fine in local host.
when I deploy the website in server .I can see the login page when I browse from IIS. But user name and password is not working.
For testing I placed a grid view in login page and tried to conncet using sql server authentication.
when I tried to use sql authentication as below

con = New SqlConnection("Data Source=15.555.10.31;Initial Catalog=ABCSYSTEM;Persist Security Info=True;User ID=TEST;Password=Pass1255")

grid view is showing error as below

Databse schema could not be retrieved for this connection.please make sure the connection settings are correct and that the database is online.

I updated databse as below ,still same error is showing

USE master;

GO

ALTER DATABASE [ABCSYSTEM] SET ONLINE