Jacklekins: So, I played Stardew Valley yesterday for an ungodly amount of time, got pretty far considering, and today I woke up to play again. I was excited to play, tried to start up the game and it wouldn't work. It was popping up in my task manager for about ten seconds and then disappearing. I was messing around in the game files for like three hours when I came across the Steam forums where people were having the same issue. Apparently, the only problem was that my headphones weren't plugged in. I plugged in headphones and the game started right up. I'm not sure why this is an issue but if you've tried everything possible and nothing is working, but you don't have a sound system plugged in, speakers or headphones, etc., just plug in a pair of headphones and it might solve your problem. This is honestly the stupidest thing that I've ever encountered but I'm just glad that it's working now and I thought that I'd share this piece of information in case some of you are experiencing the same problem.
Hope this helps!