Mailmeteor might have issues when you have multiple accounts logged in Google. To avoid such situation try the following:
Try to reload Mailmeteor. Close the add-on and open it again.
If that does not help, log out of all accounts except the one you need to send emails from. At the top right corner of the window, click Profile > Sign out. Now open Mailmeteor again, did it work?
Still in trouble? Open Mailmeteor in incognito mode (or private browsing) or using a different browser.
If the error persists, you might need to re-install the add-on:
Uninstall the add-on first. Go to Mailmeteor's G Suite page, click on the blue Uninstall button.
Then install Mailmeteor again from our G Suite page.
When an error occur, it does not impact your Gmail account and emailing campaigns. To confirm so, have a look to your email sent in Gmail.
Still having an issue and need a helping hand? Contact us. We'll be happy to help!