Hi @Corsaboy, welcome to our forum!
Have you tried charging the device for 3-4 hours? If it does not indicate that it's charging, you can try and hold the power button and volume up button pressed for 10 seconds.
If you are not able to power it on in any way, you could try and perform a software repair using Xperia Companion. This will delete all data stored on the device, including the screen lock. Keep in mind that if you had a Google account added to the device, you'll need to use these credentials to log back into the device after the reset.
Keep us posted!
