Welcome to Android Central! Have you tried a different cable and/or wall charging plug? And how long have you tried charging the phone? Leave it charging on a wall outlet undisturbed for at least 4-6 hours. Then try powering on by pressing and holding Power for 15-20 seconds.
In the future, make sure you keep photos and other data regularly backed up or synced somewhere. Phone storage (and SD storage) are not foolproof, and can fail unexpectedly.