Try this:
- unassign planting task;
- build a storage for seeds;
- wait until all seeds are delivered into the storage;
- assign planting task.

引用自 巴卡：

After being assigned planting tasks, the employees do not carry them out. In the game, after selecting crops to plant, the employees do not perform the related work, but they can complete other assigned tasks such as gathering and construction.

Thanks for reporting this issue. Even though there might be some workarounds, we would like to make sure that they're not necessary. Could you please share your save files and player log and send them to hotelgalactic@ancientforgestudio.com ?

Where to find logs/save files:
C:\Users\username\AppData\LocalLow\Ancient Forge\Hotel Galactic