Long shot but go into device manager, expand the "Processors" bit and you should see six items (may be 12), right click each one and select uninstall, once they're all gone reboot the machine (don't worry it will put them back but may put the correct amount in).Oh and it was working as an 8c 16t earlier and it is an R7 1700. Any ideas anyone?
You have to do this on some Intel systems sometimes when adding a second CPU because Windows doesn't realise it has extra cores available if the physical CPU hasn't changed, so there's an outside chance you have the same issue.