You can't do anything through Ebay who, as you know, allow 30 days to start a case and return a faulty item.
This is between you and the seller.
I think you are probably out of time to start a chargeback - most payment providers give you 120 days to open a payment dispute if the goods you buy online are not fit for purpose.
Have you tried writing to the seller (not an email) explaining the issue, stressing you are aware of your consumer rights and explaining what you expect them to do?
"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)