Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/eda0cf4b485e572d3d1ca9c1bb3e1c29.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563