Enable Sql Server Authentication Mode Over Network

Check the followings:
1. Right click the root node on Object Explorer, in Server Properties window->Security->Server authentication: SQL Server and Windows Authentication mode
2. Create a new user for login.
3. Right click the user on Object Explorer, in Login Properties window:
    3.1 User Mapping: Check the desired database to access
    3.2 Status->Permission to connect to database engine: Grant; Login: Enabled
4. Sql Server Configuration Manager -> Enable TCP/IP and Named Pipes
5. REMEMBER TO RESTART THE MSSQLSERVER SERVICE.