Yesterday installed Windows 8.1 on UEFI mode from my previously installed Windows 10 on BIOS/Legacy mode, after that my Broadcom Wireless Device isn't working, it always showing no connection found even this device is found and working properly by Device Manager. I also tried to install the driver but nothing happen, i still face that problem. Can you help me please?
I'm presuming your pavilion did not come with Win10 and you're trying to restore it to its original OS -- Win8.1, right?
So, HOW are you doing the restore? Did you use the (unreliable) Win10 GoBack function?
If that is the case, and you did not make recovery media back when it was running Win8.1, you need to consider restoring it using HP Recovery Media. That is a set of DVDs that will erase the drive, reinstalling the original OS, drivers, and HP utilities.