Try another browser to rule out a browser issue.

Try another network connection if you are using a VPN, hotspot or Starlink network.

Try another link to rule out a bad link. If you are returning an item, try starting here:

https://www.ebay.com.au/help/buying/returns-items-not-received-refunds-buyers/return-item-refund?id=...

If none of that work, try using the eBay app to start the return.