I am trying to solve the ORA-12514 error. The solution is to check if the [tnsnames.ora] the [SERVICE_NAME] is a valid service name in your database.
I can't find this path ($ORACLE_HOME\network\admin) in DB directory.
But we can also check in the preferences window which I can't find in the Oracle SQL Dev. GUI. (as shown in the picture attached)
In SQL Devloper's Connections pane right click on your database name - on a context menu click Properties and then check all the data, including SERVICE_NAME and compare it with your TNSNAMES.ora file.
Regards...