Why is my Epson L350 won't power on?

I remove the printhead and soak it in water to clean it. The water height is just a few mm exactly same level as the metal plate covering the printhead. I soak it for 2-3 hours and dry it with tissue paper. I also place it for overnight to dry in case there is any water left in there. The next day I put it back in the printer. It runs for a few minutes and then suddenly automatically power off and can't power on anymore. Any idea what is happening to my printer?