My Samsung S4 won't connect to my computer
I guess your Device drivers wasn't successfully installed in your pc

Here is couple of things you can do,:


Uninstall Kies
Go to device manager of your pc and remove/uninstall anything related to samsung
Reboot your device(optional)
Then Download Kies to your computer and while installing dont connect your s4 with pc.
After installation connect your Device and let it install device driver sucessfully. 


Hope this will Help you, For more information See this

S4 connect issue

Link 2