Resistance Order with a empty slot won't accept order. What am I doing wrong?

Resistance Order with a empty slot won't accept order. What am I doing wrong? - Person choosing document in folder

Here is a screenshot to explain the situation: enter image description here

When I try to drag those available orders to the empty slot (red arrows) they won't move and make a bip sound like "can't do it".

There is no explanation why it won't accept. I don't know what to do.

What am I doing wrong?






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Resistance Order with a empty slot won't accept order. What am I doing wrong? - Empty white photo frames on wooden surface
Resistance Order with a empty slot won't accept order. What am I doing wrong? - Person taking white paper from folder
Resistance Order with a empty slot won't accept order. What am I doing wrong? - Empty apartment with packed carton boxes before moving





fDeck: Flight Instruments Empty Slot Tutorial




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Images: Anete Lusina, Angela Roma, Anete Lusina, Ketut Subiyanto