There was a change in the buildFromContent function parameters which we announced a while ago.
Weren't you getting a Declaration of ... must be compatible with .. error?
public static function buildFromContent( $subject, $htmlContent='', $plaintextContent=NULL, $type = 'transactional', $useWrapper=TRUE, $emailKey=NULL, $trackingEnabled=TRUE )
vs
public static function buildFromContent( $subject, $htmlContent='', $plaintextContent=NULL, $type = NULL, $useWrapper=\IPS\Email::WRAPPER_USE, $emailKey=NULL, $trackingEnabled=TRUE )