Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/df75583d963d883023dc5d8d96f5d1e2.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563