You have been told not to send it.
My advice would be, don't send it. You will only be down postage costs if you send it.
Cancel using the reason 'buyer asked to cancel' and relist it.
If you do send it, the buyer may well find an excuse to return it. (It doesn't match the description, arrived damaged etc.
As a private seller, you won't pay any Ebay fees, unless you had upfront listing costs.
Never try to force an unwilling buyer to go through with the deal. That is just asking for trouble.
"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)