I have the same problem and tried the steps up above and tried it on a different computer as well with no success. Any help on solving this would be great.
If you’re still having trouble fully authenticating and getting your WooCommerce integration connected to Klaviyo, I would recommend double checking your permissions in your WooCommerce backend as well.
If you’ve checked and made sure you have the right permissions, I would encourage you to reach out to our wonderful Support team. They’ll be able to take a closer look into your account to see if there were any additional errors or clues preventing the connection from being established.
I have the same issue, I’m not sure if the problem is that my ID looks like this ID: companyId instead of my Klaviyo’s API KEY, and every time I try to integrate, WooCommerce creates a new API KEY (write/read). That could be the root cause of the issue? (not sharing with WooCommerce the Klaviyo’s API KEY)