Why isn't the sound working in Windows 10 with BootCamp installed on MacBook Pro Mid 2012

So, I've recently had a huge hard drive error then I formatted the disk and installed Windows 10 I downloaded BootCamp software 5.1.5621 (which is the version for this computer) and my audio has not worked. I have used Windows 8.1 in the past without Activation but that was a few months ago. I erased it 2 days after I put it on the computer but all drivers worked fine on there. Although I did plug in a USB headset and audio installed and worked fine! Please help! I've even reinstalled BootCamp!