The Manors are finally working in C4, but.. the buyback screen (tally up indigenous product) is strange, and it does not seem to allow you to sell your crops.
I checked whether any manor had bought any crop back, and none of them had. So, either no one but me has tried to sell, or they are unable to sell as well.
Whether the seller used the official client or not is another matter entirely. ;)
Personally I find the new windows less straightforward to use from the initial look that I have had. I'll only be able to confirm or refute this when the manors come back up after siege weekend. Still, nothing will be done if NA players dislike them anyway.