I found out Social Login (Login with Facebook) is not working while Hummingbird caching is on. I had to deactivate it to let user login with Facebook. I contacted YITH side and their response was:
"you should contact the cache plugin developer and ask them how you can exclude
wp-content/plugins/yith-woocommerce-social-login-premium/includes/hybridauth/ and the cookie ywsl_wp_session from their cache system"
I need guides on how to achieve that.