Web Application not able to connect to db

Stack Trace:

[Win32Exception (0x80004005): The system cannot find the file specified]

[SqlException (0x80131904): A network-related or instance-specific error occurred while establishing a connection to SQL Server. The server was not found or was not accessible. Verify that the instance name is correct and that SQL Server is configured to allow remote connections. (provider: SQL Network Interfaces, error: 52 - Unable to locate a Local Database Runtime installation. Verify that SQL Server Express is properly installed and that the Local Database Runtime feature is enabled.)]

I have deployed my database to the server using ssms 2016, and added the connection string to my web application that is deployed.However I received the following error message posted above.I suspected that the application cannot reach the database.

I tried changing the connection string several times to no avail