Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/4a538a11055826b9627e5b0305e345c8.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563