Following are few of the points which will help to debug the issue.
1) Enable debug by adding following in your wp-config.php file before /* That’s all, stop editing! Happy blogging.
And then try to activate the plugin again. This will create a debug.log under wp-content folder. Check for cf7 google sheet connector error if so send us the file at firstname.lastname@example.org
2) Check the log that is created by CF7 google sheet. For that click “View” from goggle sheet integration page. Let us know if there is any error we will assist you.
3) Check what other CF7 extension you are using. Deactivate one by one and check if there is any conflict.