Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/886bab5b7f04b4e3b5817c5bbb8ee894.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563