OJS reviewers assigned but review request mail failed

We assigned 3 reviewers for a manuscript. We have been noticed that the review request mail failed to send. Now when we try to send the email again, we are not getting the drop-down email template to send the review request mail to the reviewers. When I click on the “Email Reviewer” under the review section, I am getting a blank page and no options to select the appropriate email

Have you see your email configuration setting in config.inc.php?

Maybe the problem in there