When you add a Gmail card to a Flow for the first time, you'll be prompted to create a connection. Connecting your account will enable you to save your account information and reuse that connection the next time you build a Flow with the connector. If you are using a non-enterprise gmail.com or googlemail.com account, then you will not be able to establish a connection for the Gmail connector or execute any Flow that contains a Gmail card.
You can create multiple connections and manage them from your Connections page.
To create a new connection from an Event or Action card:
Click New Connection.
Enter a Connection Nickname for your G Suite account. The nickname can be the actual name of the account or a generic nickname.
Note: gmail.com and googlemail.com accounts are not supported.
In the OAuth window, enter your Google account and password information.
On the card, authorize access to your Google account by clicking Allow.
The app’s use of information received from Gmail APIs will adhere to Google’s Limited Use Requirements.