Happy to provide what answers we can, even though this is a 4 year old purchase.

That said, if things were working fine before and now they're not, its likely a general website question and not really a bug with ecommerce. Maybe start with your webhost, see if something has changed there..? Have they upgraded PHP perhaps? Sometimes that causes errors if you haven't also upgraded concrete5.

If you can post some details here on what's going on with ecommerce, we let you know if we've seen anything similar.

You can always find freelancers who can help in the job forum as well:
http://concrete5.org/community/jobs...