Do not wait for a replacement and do not exceed the time period of 30 days to claim for your full refund.
Proceed this way now.
If a reasonable time has passed your item's last estimated date for delivery, and you have not received the item, then, if the seller is not being helpful, go right of the item purchased, and from More Actions select.... I Have Not Received My Item.
If you are not fully refunded within 3 days, you must escalate the case on day 4 or within 30 days from opening the case, and eBay will step in and force the refund.
Do not close the case early for any excuse or promise the seller may give, and do not forget to escalate.