Was this a Simple Delivery transaction?

Ask the buyer to open a case for a refund stating ' damaged in transit'.  eBay will refund the buyer and you get to keep the payout.

Be aware, you are actually using the wrong account to sell on.  A Private account the one you're using is for selling your unwanted, used items,  say a garage/ attic/ wardrobe clear out.  You are selling all new items and in  quantities so should have a Business account.  eBay will note this once a case is opened, doubt they'll be keen to refund when this is a Business seller's responsibility.

It's easy to switch your account to the correct one as below:

1. Go to Account settings in My eBay.
2. Select Personal information. 
3. Select Edit next to Account type. You may be asked to sign in again.
4. Select Confirm to upgrade to a Business account.
5. Specify whether you operate your business as a legal entity or as a sole proprietor and select Continue.
6. On the following page, enter your business information such as name, contact information, and returns policy. Then select Save.

Probably best to use a PC / laptop for this,  and not the app or mobile browser.  Chrome seems to work best on eBay.

@mad0903