The Global Shipping Program is a Seller Protection program which has few advantages for buyers.
The seller has only to send your purchase to the GSP plant in Erlanger KY, and his responsibility for delivery ends.
YOU are still protected by eBay's Money Back Guarantee for 30 days from that last estimated date for delivery.
Which was November 27th.
Oops.
YOU ARE STILL PROTECTED!
If you paid with Paypal you have 180 days from Payment to start an Item Not Recieved dispute through PP.
State in the Dispute that this was a GSP shipment. Your seller did nothing wrong and will not be penalized.
GSP has no emotional concerns and good insurance.
If they cannot prove delivery, you will be refunded.
If you did not use PP to process your payment, go to the credit card you did use and ask about a chargeback. While card policies differ, most allow more than a month for chargebacks. Again, explain that this is a GSP shipment.
One complication, and why it is very important that GSP be refunding, is that you paid them to cover import fees (duty and sales taxes). Only the GSP can refund these, because the seller never saw them and because you technically did not pay them- you paid GSP to pay them.
The basic reasons for the delivery delay is the mess made by COVID, flooding, heavy holiday shipping, and washed out highways, plus a shortage of truckers and flight crew.
But you are covered.
In future, mark the last date for delivery on your calendar and claim with eBay promptly. They really are the easiest to deal with-- unless their deadline passes.