Unlike Poshmark/Mercari/Depop/Vinted, eBay has an official OAuth flow. You'll sign in on eBay's own page; eBay sends Closo a token; Closo can list and edit on your behalf.
1. Marketplaces → check the region (US) on the eBay card and click Connect Ebay.
2. eBay's sign-in page opens in a new tab.
3. Click I Agree. eBay returns you to Closo. Done.
Watch the step-by-step video guide