how many time I have to open a case?

[pjcdn2005]

if you are asking how much time, you have 30 days after the last estimated delivery date to open a case on eBay.  If you used PayPal you have 180 days from the payment date to open a case there.

[reallynicestamps]

You can only open a Dispute on each transaction once.

If you close a Dispute, you cannot reopen it, nor can you change it to a Cancellation.

If you close a cancellation, you cannot reopen it nor can you change it to a Dispute.

If a seller tells you that he cannot refund you until you close the Dispute, he is LYING to you.     

If a seller told you to close a dispute to get your refund, you can go to Paypal and start a new dispute there. 

Do you have more questions? Just click on Answer on your own post.                                 

[ypdc_dennis]

For what reason?

Item-Not-Received is for 30 days after estimated delivery time through eBay.

Second line of protection is 180 days from time of purchase if you paid via PayPal.

Final line of protection is if you paid using a credit card (check to see what protection they provide, as it varies between cards).

Item-Not-As-Described protection starts with eBay when you get the purchase.