assemble computer parts

We are building our own workstations. I got all parts, send them to Fry's to assemble. But they said the Ryzen and motherboard does not post. Since I bought the combo from Amazon: https://www.amazon.com/gp/product/B074QP7WBC/ref=ask_ql_qh_dp_hza they sold a lot and have high rating, I believe these two parts should work in principle. Some people have similar problems: https://community.amd.com/thread/219286#2835342

I think it may be Fry's technical problem, we want to find someone have experience building computer from parts.