Dell U3014 User Manual page 26

The default out of factory setting in the U3014 is DP1.1a.
To enable MST connection please use only DP cable as provided in box (or other DP1.2 certified cable) and change the DP setting to DP1.2 by performing the below steps:
A) Monitor is able to show content
1. Use OSD button to navigate to Display Settings
2. Go to DisplayPort 1.2 selection
3. Select Enable or Disable accordingly
4. Follow the screen message to confirm selection of DP1.2 or DP1.1a