Hi, thank you for contacting JustAnswer.com. My name is Russell. I will do my best to provide the right answer to your question.
Obviously, you should try powering it On while holding down the buttons for a hard reset.
Have you done that? if not, I will provide details as needed.
If you have done that, or if you do that, and the phone still does not get into working order, then the phone will unfortunately have to go to a repair shop, or be replaced.
(Unless the phone was gotten wet recently, perhaps, in which case, it will need to be left Off and without its battery too - if the battery is easy to remove - and in a dry warm place for at least 3 days, to prevent permanent damage to it.)
Let me know, so that I may advise you further as needed, please. I hope something good can be made of this problem. Thanks.
That's the right way to proceed, I think.
If you are not just letting it rest and dry off for overnight, then you may well invest at least 3 days in the process.
Thank you for letting me know.