Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/7b0b0c4bf8d447d985ff80a541bf9785.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563