Resolving ORA-12705 Cannot Access NLS data files or invalid environment specified

Problem 

While using SQL Developer you’ve encountered the error ORA-12705: Cannot Access NLS data files or invalid environment specified, but don’t know how to resolve this issue. Below are step that should be taken to resolve the issue.

Resolving ORA-12705 Cannot Access NLS data files or invalid environment specified 

• Locate and open your SQL Developer folder.
• Locate the /bin/folder by browsing to the location sqldeveloper/sqldeveloper/bin/
• Locate and open the sqldeveloper.conf using a text editor. Notepad++ works fine.
• Copy and paste and save the following lines to the file:

# Resolving ORA-12705 Cannot Access NLS data files or invalid environment specified 
AddVMOption -Duser.language=en 
AddVMOption -Duser.region=US 
AddVMOption -Duser.country=en

• Restart SQL Developer
• For a working example on how to fix/resolve the error ORA-12705: Cannot Access NLS data files or invalid environment specified, please see the animated GIF. Below.

Conclusion

Applying the fix above will fix the error : “ORA-12705: Cannot Access NLS data files or invalid environment specified”. If the error still persist, please ensure that you follow the steps precisely and all the files are properly saved.