Magento2 Integration with Klaviyo – Integration got successfull but after 1 hour it the sync failed

I’m using magento 2.4.7-p6. Recently migrated from Mailchimp to Klaviyo and everything works smoothly.
So from last day I’m facing a problem regarding the Klaviyo Integrations with Magento

When I click reAuthorized from Magento Integrations sections, The connection successfully build but after an hour the Sync Failed. The Klaviyo dashboard says https://ibb.co/WW4Trbs0

I manually have to reAuthorize it everytime. Why it is not refreshing a token? What could be the possibilities?

I’m using Nexcess server.