If you receive an item that is not as described in the listing,you have up to 45 days from the time you paid to open an item not as described dispute.
If you don't receive the item,the same 45 day time limit applies for opening an item not as described dispute.
In any case,the first step is to contact the seller. If the seller refuses a refund or doesn't return your messages,open the appropriate dispute.
In the case of an item not as described,you will have to return the defective item with delivery confirmation at your expense and will receive your refund when the delivery confirmation shows that the seller has received the returned item.
Open the dispute no later than day 43 to be safe.
You have 60 days to leave feedback and DSR ratings.
Here's the page about item ot received or not as described disputes.