What exactly model do you have? Because not all the f2a55m can support the A10-7850K, the cpu is the fm2+ socket but some of f2a55m is the fm2 socket. Check your MB from gigbyte website to see it can support the A10 or not.
like GA-F2A55M-HD2 v1 and v1.2 does not, but v3.0 does. You can check it under "support and downloads" and choose the version on the top. http://www.gigabyte.com/products/product-page.aspx?pid=4782#
Its completely compatible with fm2 and fm2+, the board is. It was a deal from microcenter for both together, we've switched out between two different ones and its doing the same exact thing. Everything works, it is not giving us any beeps as to what the issue would be, we tested the ram, the graphics card, everything. We tried onboard vga, onboard dvi, a different graphics card. It won't show video and it won't bootup correctly, no bootup beep.