Archive Pages not working

When i click on archive link its showing the below massage any help is appreciable.Thanks in advance.
You don’t have permission to access /grav/grav-admin/archives_month:jan_2016 on this server.

Set your folder and service running users rights correctly. Issue is most likely that it creates file that service has no rights to use or it simply finds that it cannot create file because service user does not have sufficient rights. Check folder permissions.

It could also be missing the .htaccess file - is it there in the Grav root folder?