Note: if you are using TNSNAMES.ORA file then make sure the file is under the correct location, then test the database connection with SQLPlus to make sure the TNSNAMES.ORA file is working.
Note: if you are using TNSNAMES.ORA file then make sure the file is under the correct location, then test the database connection with SQLPlus to make sure the TNSNAMES.ORA file is working.