Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/652fd0de71c0ecc0b5d1a2fea4f0d65d.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563