Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/5a2ae00068738012d2c3a8faaae0d6cb.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563