There are a couple of steps that you can take to remedy this.
The first step is to turn on the mail debug logs.
mail.debug=true in the advanced settings on the tenant.
The second step is to confirm that you are able to send a test email.
Additional details can be found in our troubleshooting guide.
https://fusionauth.io/docs/v1/tech/troubleshooting/#troubleshooting-email.
Finally, Gmail, especially with recent security upgrades, may require you to have MFA enabled or not allow apps to access its SMTP servers unless specifically allowed.
I was able to get a test email to send from my personal account by generating an "application password" and using SSL to send.
https://support.google.com/accounts/answer/185833
https://support.google.com/mail/answer/7126229?hl=en
I hope this helps!
Thanks,
Josh