Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/011f0f7a0da5aadd1d88ec2f83cd7c63.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563