Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/0f2d19ec28327b928d3f7c1ad1c98916.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563