Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/2c1f2766d85dc430a5e5b8e394d25eeb.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563