Hey @Vaibhaav,

The error messages you're encountering indicate a memory allocation issue within your Magento 2 installation. While you have generated a full-access Klaviyo API key, the integration process seems to be exceeding the allowed memory limit.

Here's how to address this:

1. Increase PHP Memory Limit:

The most common solution is to increase the PHP memory limit for your Magento 2 store. You can achieve this by editing your php.ini file or through your hosting control panel.
A recommended starting point could be 256M or 512M, but adjust based on your server resources and the complexity of your Magento store.

2. Review Klaviyo Permissions:

While you mentioned a full-access Klaviyo API key, ensure the specific permissions assigned to the key grant access to the necessary functionalities for the integration. Double-check Klaviyo's documentation to verify required permissions.

3. Debugging & Klaviyo Support:

Temporarily disable other Magento extensions to rule out conflicts.
If increasing the memory limit doesn't resolve the issue, consider using debugging tools or logs within Magento 2 to see if there are more specific error messages related to the Klaviyo integration.

4. Klaviyo Support:

If the above steps don't work, reach out to Klaviyo support directly. They can investigate further based on your specific account, Magento 2 configuration, and the Klaviyo integration process.

Additional Tips:

Consider contacting your web hosting provider for assistance with increasing the PHP memory limit if needed.