Hello @perosak
Sorry for the trouble.
Have you updated the plugin version to latest? If not please upgrade and if already updated then do the following.
1. Click here
https://myaccount.google.com/permissions
there you will get Third-party apps with account access.. Under Third-party apps with account access, You will see various connections, which you authenticated. You will notice GSheetConnector connection as well, click on it and remove access manually while clicking and then again reauthenticate from plugin settings.
This needs to be done after plugin update, after reauthenticate check again above link, you will see APP again with all the required permissions.
2. If in case still, data is not saving in sheet, then check to debug log, make sure it should be enabled from wp-config.php.
Refer from here and all the other points too.
https://mailchi.mp/44985dea65c0/reauthentication-needed-for-gsheetconnector-after-update
3. Make sure, you must have to add Google Sheet Name, Sheet ID, Tab Name and Tab ID correctly as specified in link below.
https://www.gsheetconnector.com/docs/cf7-gsheet-connector-free/how-to-connect-a-google-sheet-with-cf7-forms
Then let me know if still have any issues, feel free to message me with screenshots of an error log, configuration page of GoogleSheet Tab and Google Sheet Columns to check and verify.