Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/d4ad776e7f1f1fc5f118e0f0072c18ab.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563