Things to check.
That you have connected the extra power required to the card via your power supply unit of the system.
That your eight pin 12v E-atx is connected to the motherboard from the PSU.
Check in the bios that you have set your primary default display adapter to initialize first to Pci-e in the order of graphics devices.
That you installed the latest version of the Ati driver from Amd.
And also make sure or re install all direct X files.
From here for windows, from Microsoft.
https://www.microsoft.com/en-us/download/details.aspx?id=35&44F86079-8679-400C-BFF2-9CA5F2BCBDFC=1
White dots down clock the card by 50Mhz to 100Mhz. Gpu and Mem.