Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/5bc1fb615bf30d6b2b92041a661d4b3f.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563