I had the same issue with my 2011 Mac Mini, and I read somewhere online about the reflowing trick by putting it into the oven for about 10 minutes at 150 - 175 degrees Celsius. As it was my last resort, I couldn’t use it in a few months, I completely disassembled it to just bare motherboard, put it into the oven, heat it up, let it cool after, and it works now! It has been for a few months. Hope this helps you.