Since the new xpac came out, I haven't been able to sell seeds in my inventory. It doesn't matter if they come from Patchy, seed packs that I get at Harvestfest or seeds packs that I buy. You used to be able to drag them from your inventory to sell them. No longer.
You can sell them in your household inventory. This is a pain in the neck because you have to place each seed on the ground, then sell them individually in your inventory. Kind of a pain if you are like me and collect a lot of seed packs at Harvestfest.
The other thing is that if you drag the seeds into your household inventory and then sell them, you will get 3-5x their price. I've seen seeds that list for 3 simoleons sell for 14 when I drag them from the household inventory.
So I'm not sure if this is a game wide bug or just something weird for me. But if you are playing some kind of challenge game, it's a potentially game breaking exploit.