I have been running into the exact same issue with items coming from China since the middle of September this year. Unfortunately more than 50% of my orders have been no shows...the standard answer from ALL Chinese vendors in such cases is the item was rejected by customs.
I suggest that you start the process of communicating with the vendor through the paypal claims system, you do not have to escalate the transaction if the vendor provides you with refund. You must do this before the 45 days has expired
By using paypal claims system, it will allow you extra time (beyond the 45 days on ebay) to straighten things out with the vendor directly, and still protect your purchase rights.
In the event your vendor is still not co operating to your satisfaction, you can very easily escalate your claim with one click, and then paypal will take over, investigate your claim, including reviewing ALL emails exchanged between you and the vendor, and provide a satisfactory result.
In my experience, the vendors respond rapidly through the paypal system. And those that do not, paypal has completed claim investigations and refunded monies generally within 48 hours of escalation of said claim.