Fix WP Plugin Email Confirmation Not Sending

We have a WP booking plugin; and use FluentSMTP to send out emails. Some emails like forgot password, and message notifications work - however, booking confirmation emails and few other emails are not sent out as they should be. Need someone who's experienced in this area to take a look and fix this - should be pretty straightforward if you know what you're doing because other emails are already working, so probably some settings or a glitch somewhere.

Need this done in the next 24 hours - you get extra bonus if you complete within 24 hours.