Stallion with the issue:
https://horseeden.com/horse.php?id=21515285

I put 6 straw offers out to the same account for 6 different stallions. 5 of them worked without an issue, but I got the following error for the 6th,

Initially he only had 10 straws from past game years. I tried pulling an additional 4 and placing the straw offer again and still received the same message.

I can however list his straws publicly in the store and that worked without issue.

I tested trying to place another straw offer to a different stable, trying a different price, and different straw quantities, none of which would work for the linked horse.