no payment email

I have purchased the Personal Extended Version and have a problem with sending e-mails.
When customers book a date, an email of the request goes out successfully.
However, when customers pay for the booking via PayPal using the plugin, neither a booking confirmation nor a payment confirmation goes out.
Only the request is sent before payment is made.
If a booking is cancelled, an e-mail about the cancellation is successfully sent.
However, I absolutely need a confirmation e-mail after successful payment via PayPal.
PHPMailer I have switched on and tested and switched off and tested. This changes nothing.
Nothing gets into the spam folder either. I have also tried it with other e-mail addresses.
The URL is: https://ferienwohnung-schlummi.de/fahrrad/

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