At a glance, it looks like you cancelled a few sales due to being out of stock, which gives your selling account a damaging defect for each order cancelled, it doesn't take many to heavily impact your account.
All you can do is to sell as many items as possible as quickly as possible and keep an eye on your seller dashboard and metrics, this eBay guidance page explain show they work and how to monitor them:
https://www.ebay.co.uk/help/policies/selling-policies/seller-standards-policy?id=4347&st=3&pos=2&que...
