Hello @Think,
Thank you for sharing your question with the Community.
It is great to hear you have already taken steps to resolve the issue. In addition to these steps I recommend checking your inbox filters to ensure this message hasn’t been filtered elsewhere, and also your firewall settings to ensure the email hasn’t been deferred or blocked. If you are using Gmail, I recommend looking at the “Promotions” tab for this message. Also try searching for “Confirm Your Klaviyo Email” in your inbox. If none of these solutions resolves the issue, I would try setting-up the account with a net-new email address. If it works for another email, and you still want to use the original email as the primary email address on the Klaviyo account, you can add the original email to the Klaviyo account as a user and then transfer account ownership to this email.
Hope that is helpful!