how to use “remove connection”

Hi,
I have a WP Mail SMTP on my client website, using the Gmail for delivery of the contact form. I discovered one cause of the error is with the PHP version. It still did solve the problem. I also learned that my client have changed the Gmail password. How do I use the “remove connection” button to get the email delivery issues fixed.

Is there a need to renew the client secret code.

Thanks for your kind assistance