Thank you for the recommendation! Unfortunately it is a bug, as listed here
https://thesimsmedieval.fandom.com/wiki/Bugs/Glitches. I've been playing the game since I was a kid, so I do know that you have to use the doctor/mage/assassin/etc to collect resources other than wildflowers. I know that in the past others have used Carrigon's shop mod to get high level resources that are no longer collectible, or ChickieTeeta's version for pirates and nobles. All of the base game compatible versions that I know of aren't on accessible sites anymore, that's why I'm asking.