Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/2a4ea7d01f18e04d9cff80e2c8e28aba.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563