If you are using a firewall on your android the android internal internet check fails. The Wifi connection shows a little "x".
Some syncs are not initialized by android, which means you have to disable the firewall and start the sync manual.
You can disable the internet check so that the sync starts normally:
settings put global captive_portal_detection_enabled 0 settings put global captive_portal_mode 0 settings put global wifi_watchdog_on 0
After executing this commands you have to reboot you android.