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If you installed Express edition, your sid or service should be XE, so this error implies the database isn't up.
Open a command window and type
This should show what services are running (if any).
This will show the connection definition being used. It is what you would expect? Are host, port and sid or service correct?
Do they match what you have entered for your connection definition in SQL Developer?
If the definitions seem OK, try using the start menu options to stop and start the XE database and try connectiing again.
Just try following the below steps
1. Check if the ORACLE_HOME and TNS_ADMIN variables are set properly(any change would require a restart).
2. Check if the correct driver is installed.
3. tnsping any SID and see if there is a response.
4. Check if the file TNSNAMES.ORA and SQLNET.ORA are in the correct location with the correct entries
This should resolve the issue