I don’t know if the heat sink only is available. Makes me wonder if something else is wrong with the board. I would not trust it. I would get my money back through eBay.
MZ790A Bios 2002, GSkill F5-8000J3848H16GX2-TZRK, 13900KS, EKWB D5 TBE 300, Seasonic Prime TX-1600 ATX 3.0, Asus Strix 4090 w/ Optimus block, Phanteks Enthoo Elite, Asus Claymore 2, Asus Gladius 3, Asus XG349C, Samsung 990, Windows 11 Pro