To reset OSX Network preferences to system default follow below steps.
The first thing you want to do is reset your location.
Go to System preferences > network, then in the top select location and then edit locations.
Use the (-) to delete the current location,
Use the (+) to add a new location,
With new location try to connect to your internet.
If Step 01 does not work completely reset your networking connections by going to:
Macintosh HD/ Library / Preferences /
Drag the ‘SystemConfiguration’ folder to the trash or just delete it but do not empty the trash just yet. You may need this folder in future.
Now Restart your computer.
Note: Don’t worry Mac will create new ‘SystemConfiguration’ folder with default settings & preferences. When you log back in all of your network and bluetooth connections will be reseted. Now try to reconnect to your network.
Tip: if Step 02 doesn’t work or doesn’t have an effect you can replace ‘SystemConfiguration’ folder with original folder which is currently in Trash to rollback previous network settings.
Hope it Helps,
Thanks & Regards