1) Check whether you have not used contact form field name in capital letter and also not use underscore ( _ ) & Special character.
2) Double check sheet name and tab name.
3) Check on which google account you have integrated. Is it where you have saved your google sheet ?
4) Check the log files for any error that is click on “view” link under google sheet connector.
5) Lastly enable WordPress debug and see if there is some log for google sheet connector.