This indicates the domain has a problem with its "setup". As is mentioned in several other threads on this forum, you can often correct this yourself by going to the "Control Panel", selecting "Manage Domains", clicking the "Edit" link on the far right end of the line for the domain in question, and hitting "Save" (there is no need to actually "edit" any settings).
Even if you did not "edit" anything, this should cause the httpd_conf file to be regenerated, and it often "fixes" the problem.
If that doesn't work, it will require DH SUpport to get involved. Of course, you can generate a Support Ticket at any time without trying the "fix" described above; some just like to see if they can fix it themselves and avoid the wait for a Support response.Good Luck!