Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/3f3c8f3848b92b0db8ced3608decc0e0.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563