Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/0aa95c9abd15d1c5d2fd5926e1ef6d0d.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563