In continuation to the previous reply you have got, if the issue persists after all that steps, I would suggest you to reinstall the drivers. I have included the link for your convenience.http://dell.to/n8mu1O
The link comes with the steps to install the drivers and this should help you fix the issue. If the issue persists, I would recommend you to contact our tech support over the phone. If you have any concerns getting help over the phone, reach out to us at @dellcares on twitter or facebook.com/dell, we would be glad to help.