I've been using Zen Cart for 6 months. All was well until two nights ago. When customers place an order, they're no longer able to access their downloads, they're not notified that their order was processed, nor am I.
PayPal payments are still received, but customers can't download their orders.
Also, AFTER the problem started, I ran an upgrade. At this point, I'm getting an error message: Your database appears to need patching to a higher level. See Admin->Tools->Server Information to review patch levels.