I think this could be the problem. Google the CPUs and chipset and look at the Intel pages on them, which should list compatibility. It's quite possible that CPUs which fit the same socket won't work with a different chipset.
Also check the mobo maker's website for the latest BIOS and update it, if possible.
And finally, yes, it's quite possible that you've been sold two duff CPUs unfortunately, especially if they're off eBay from a private seller.
Thank you for the response. I have visited the official ASRock support site a while back but they stopped updating it a while ago. This board has had many unofficially supported CPU’s and custom BIOSes since ASRock abandoned it.