If you get no joy from the seller, you have 30 days in which to claim 'item not received' from ebay.
(by the way, it's not your responsibility to chase Evri, it's the seller's ...)
Do not let the time go over the 30 days whatever the seller may tell you!
When you open an 'item not received' case, the seller has 3 days to respond and sort it out. At the end of those 3 days, if you've not got the item or a refund, you can 'escalate' the case and ebay will force the refund.