Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/ef2d3445b83e4a159a80e291818c0f61.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563