Duplicants will not use farm station to create micro nutrient despite all prerequisites being met: Farm Station contains 50 kg of fertilizer, plants can have micro nutrient applied (bristle blossom and grubfruit plant), and duplicant has Crop Tending skill, and duplicant is locked in room with no other tasks (ie, duplicant is idle). Disabling and re-enabling the farming station does not resolve the issue, restarting the game does not resolve the issue.
As you can see, there are no errands to craft additional micro nutrient and Harold is idle in farm room.
Build a Farming Station, and eventually it will stop working. Reloading does not resolve the issue.