Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/3b7a0ff7b9dfc56cba532d70f13a29be.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563