Assuming your 30-day Ebay MoneyBack Guarantee time has since expired, go to Paypal and open a Case for Item Not Received there. Escalate immediately, as you have already attempted to contact the seller.
DO NOT accept an offer to replace from the seller no matter how tempting that may sound. That rarely if ever ends well. Consider it only if you've dealt with this particular seller in the past and trust them to keep their word and the item can be sent with tracking that shows delivery in a week to ten days. The 'offer to replace' is often a stall tactic. And don't be coerced or cajoled into Closing your Case before you see that refund. Some less-ethical sellers will try that one too.
Once you have your money refunded to you, try to purchase this item again. It's up to you whether you want to order it from the same seller, or another.
If the original item shows up in five months, you can always repay the seller via paypal.
EDIT:
Wait, RETURNED ITEM? You have to send it with tracking. If you didn't, there is no refund for you. The only thing that might save you there is if the seller either told you not to return it with tracking, or didn't send you money for a tracked return if it was a case of Significantly not as Described.
We need more details.
