I’ve had issues like that using the app and or clicking right from an offer email. Try logging in directly from eBay.com and see if that helps.
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Yep, log into eBay website or the app and check in the notifications and messages section. If you were emailed you should also have a message and a notification to your account directly. Clicking on the link in the message or notification should link you to the item offer. Be careful though as you spotted its easy to click back and forth and wind up at the item advert paying the full price. I fallen foul of that once.