Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/abf4f474ba9a46b1dd8c29477a3f39f9.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563