USPS missed expected delivery date, Ebay said "guaranteed delivery" by today, haven't got the package. What should I do? Says "In-Transit"?

Update: This is what it says right now (latest)
"September 8, 2018
In Transit to Next Facility
Your package is moving within the USPS network and is on track to be delivered by the expected delivery date. It is currently in transit to the next facility. "
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