Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/63a6d07f8d8f55d000f9df0f0e9c02ae.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563