If it was the item you left a negative for, it looks as if you waited too long before opening a case.
The item was covered by the Money Back Guarantee but you have to follow the process.
You can open an 'item not received' case when the item is a day overdue.
You have to open a case within 30 days of the latest estimated delivery date.
If the item doesn't arrive and the seller doesn't refund you, then you must go back to the case promptly and ask Ebay to step in.
Messaging the seller more than once is pointless. You have to deal with this by starting a case with Ebay.
"There are two ways to be fooled. One is to believe what isn't true; the other is to refuse to believe what is true.”
Søren Kierkegaard, Danish philosopher (1813 - 1855)