It's an H170 board which supposedly should allow a 7th gen. The H170 doesn't allow for an OC which the k skew get's most of it's benefit from. You can still bclk I believe but not sure. Have you updated the BIOS? there is a new one that came out two day's ago, none of the updates mention 7th gen compatibility. Considering this is an AIO tower I don't think it's geared towards tinkerers so it might take them a bit to catch up on BIOS, that is considering the newest BIOS doesn't already work.
The latest BIOS/UEFI is 2101 released feb 7th 2017
update that with your previous cpu in place then try the swap again.
https://www.asus.com/us/Tower-PCs/ROG-G20CB/HelpDesk_Download/