I have the same error using php 8.
php error log shows:
[17-Sep-2021 12:33:06 UTC] PHP Fatal error: Declaration of IPS\bouncer_hook_Email::send($to, $cc = [], $bcc = [], $fromEmail = null, $fromName = null, $additionalHeaders = [], $autoSubmitted = true) must be compatible with IPS\_Email::send($to, $cc = [], $bcc = [], $fromEmail = null, $fromName = null, $additionalHeaders = [], $autoSubmitted = true, $updateAds = true) in /home/sss/public_html/init.php(902) : eval()'d code on line 83