Hello,
It’s not a fatal error, it’s just a warning that comes from the Cookie notice plugin. Try to downgrade plugin to the previous version as described here https://www.8theme.com/topic/whats-mean-warning-call_user_func_array-expects-parameter-1-to-be-a-valid/ or https://www.8theme.com/topic/xstore-cookie-notice-plugin-not-working-after-update-to-v2-0-2/
Regards
