Red Dot Illuminated on the Power Button after Cleaning.

So, I have an Xbox 360 Slim that I grew up on. It has all my saves and it’s a great box of memories for me. I recently took it apart to clean the dust, but when I put it back together I forgot to install the WiFi card by accident. No big deal, right? When I started it up I realized something was awry. There was one red dot in the middle of the consoles power button. I then saw the WiFi card on the table and realized I was an idiot. So, I put the card back in and tried again. It still wouldn’t boot. Do I have to clear some sort of error on the console? I really wanna fix this thing, and have been trying to fix it for a while, and I’m finally stumped. Any help would be EXTREMELY appreciated.