Hello Wayne,
Welcome to Microsoft Community. I will certainly help you with the issue that you are facing. This issue usually arises due to a driver conflict or when there are hardware issues. I would like to ask you:
- What is the make and model of your computer?
- Have you updated all the drivers from the support website of the computer manufacturer?
- Is your computer compatible?
To diagnose and resolve this issue, try the following methods.
Method 1: Update device drivers
This issue usually arises due to outdated drivers or driver conflict. I would recommend you to visit the support website of the computer manufacturer and download the latest drivers available for your system model. Make sure you upgrade the chipset and graphic drivers along with the system BIOS.
Disclaimer: Modifying BIOS/ complementary metal oxide semiconductor (CMOS) settings incorrectly can cause serious problems that may prevent your computer from booting properly. Microsoft cannot guarantee that any problems resulting from the configuring of BIOS/CMOS settings can be solved. Modifications of the settings are at your own risk.
Method 2:
Refer to the section “Fix problems” from the following link and see if it fixes the issue.
http://windows.microsoft.com/en-us/windows-8/project-wireless-screen-miracast
Also refer,
**Windows 8.1 on your big screen with Miracast**
Hope this information was helpful. Let us know the results of these methods once you have tried these methods.