Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/59a03d3ac2b6673d27086b6d2c8f68d9.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563