Klaviyo Integration with default magento 2

I want to integrate Klaviyo with default Magento 2.4, but I'm having trouble with the integration part. It appears to

error 1) In order to finish configuring this integration, please setup or log in to your third-party account. (And already possess a Klaviyo account).
error 2: Klaviyo cannot establish an OAuth Handshake connection with the Magento Server. Verify that /oauth/token/access and /oauth/token/request are both reachable.

Additionally, it should be noted that the integration status is showing as inactive. Could you please advise me on how to fix this?