Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/a8ea6001ce4d5d8a47043d43f1d14055.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563