LG Dishwasher will not power on.

Hello everybody,

My LG dishwasher (model #: LDS5811BB) will not power on. Right now the bottom of it is filled with smelly water.

My cousin told me that its probably the main control board. I saw this video on youtube: Order parts for Appliances, Outdoor Power & HVAC (US & Canada) - YouTube
which shows thats its pretty easy to replace, so I'm thinking about ordering a main control board and replacing it,

HOWEVER, is there any troubleshooting that I should do to make SURE thats its the main control board that is the issue before I waste time/money ordering a wrong part???

Thanks so much! Any help is greatly appreciated!