Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/8866d84d3b2f6c12c9ce5cd16ac23b46.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563