Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/92b08f0a2a4af455ee30808e323a1dbe.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563