You do not need to speak to ebay, you use the money back guarantee and open a not as described case.
As it was digitally delivered, you should get a return label from the seller, so just return a printout of the ad. as you need evidence of returning what you bought. So long as ebay see tracked evidence of return, if no refund started within 3 days then escalate to ebay.
Seller is no doubt taking full advantage of the fact that buyers have nothing to return to get a refund. DO NOT RELY ON ANY PROMISES to send book, get a refund.
Alternatively contact your payment provider, but once you have done this you cannot go back to using ebay to get a refund.