Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/b2697c5b33b73b7afe18c936fb0f4554.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563