My package hasn't moved in the past 4 days from my nearest USPS Facility.

[gurmeetwwenba]

So I had purchased this backpack on the 23rd of August. The seller shipped it with USPS (Priority Mail 2 Day with $100 insurance). The item arrived to my nearedt sort facility on August 27th at 5:48 am and left the same day at 7:51 pm. Since then, it has never updated. It still says Expexted Delivery Date: August 27, 2015. What should I do? The seller has not replied to any of my messages. My zip code is 11365. 

August 27, 2015 , 7:51 pm
Departed USPS Facility
FLUSHING, NY 11351
Your item departed our USPS facility in FLUSHING, NY 11351 on August 27, 2015 at 7:51 pm. The item is currently in transit to the destination.

August 27, 2015 , 5:48 am
Arrived at USPS Destination Facility
FLUSHING, NY 11351

August 26, 2015 , 4:56 am
Departed USPS Facility
WEST SACRAMENTO, CA 95799

August 25, 2015 , 8:06 pm
Arrived at USPS Origin Facility
WEST SACRAMENTO, CA 95799

August 25, 2015 , 3:25 pm
Departed Post Office
SACRAMENTO, CA 95834

August 25, 2015 , 12:17 pm
Picked Up
SACRAMENTO, CA 95834

August 24, 2015
Pre-Shipment Info Sent to USPS

August 24, 2015 , 2:11 pm
Shipping Label Created
SACRAMENTO, CA 95834