I see this reported quite frequently in the forums. According to what I've read, SC shuts down the ability to buy and sell in roadside shops when they suspect something not permitted is going on with the farm.
Do you use software to automate crop growing or to play on a laptop/desktop? Maybe your farm drew their attention because lots of different locations and devices were logging into your farm. :confused:
Only SC can tell you the reason, but it seems they're ignoring your in-game reports. :unsure:

