Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/544f2f0eec40ff5ff21c6a069d14a3a8.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563