Hi, same issue here, additionally I’ve tested removing the whitespaces into the app password as I don’t know if they are relevant or not. The error message is quite vague.
Using the dedicated Gmail node is irrelevant as it requires a convoluted oauth2 setup and SMTP should work out-of-the-box.
This is perhaps some security measure from Google?
Related: Connection closed unexpectedly error during sending email via Send Email node with gmail credentials