Munin does not update result

Dear Supporters,
I’m having a server which run munin, but it suddenly stop working from Monday.

I have tried to re-copy it but it show error:
$rm -rf /var/www/munin-html/*
$su -s /bin/bash munin
bash$/usr/bin/munin-cron
[ERROR] Could not copy contents from /etc/munin/static/ to /var/www/munin at /usr/lib/perl5/vendor_perl/5.8.8/Munin/Master/HTMLOld.pm line 711.

This mean the script try to copy data to /var/www/munin-html/ but it can not.
Is there something related to the folder permission of /etc/munin/static?

Thank you.