What do I do now?
I'm afraid that talking buyers into cancelling a return is the oldest trick in the book. I hope your seller still comes good on their promise to deal with it, but by cancelling the return you have thrown away your rights under eBay's money back guarantee. Only one return case is allowed for an item, and once closed it can't be reopened. Sellers know this.
In future it's safer never to cancel a return request or money back guarantee case until it's all resolved and you have your money back.
If your seller lets you down your best hope is that PayPal (if that's how you paid) or your payment provider e.g. credit or debit card may be able to help. Or you may have some statutory consumer protection rights if the seller was a UK registered business seller. Good luck.