Vizio M552i-B2 Won't turn on

Hi all. I have a Vizio TV. Model number is: M552i-B2. The TV won't turn on. When I unplug the TV and plug it back in the standby light lights up, slowly fades out, and then stays off. When I attempt to turn on the TV nothing happens. The standby light remains off. I've tried all the standard fix-it advice you can search for easily on the internet. Including looking closely at the screen with a flashlight to see if there is a backlight problem. So far I've had no luck.

My best guess at this point is the power supply board. I took the TV apart and inspected the power supply board. There are no visible signs of failed components. I disconnected the power supply board and removed it. Then reconnected it. This was an attempt to reseat all the connectors. This did not work.

Power supply board for my TV (056.04167.1011) costs $50 to $200 depending on where you buy them from. The $50 ones come from shady looking websites. I'm hesitant to spend this much money on a component when I'm not 100% sure this is the problem. I think I'd be better off buying a new TV rather then gambling on a part.

Does anyone know a way to definitely determine if the issue is the power supply board? Or based on my symptoms, does anyone have other suggestions? Thanks.