Post Assemble Order

Hello,

NAV 2016

I have a Sales Order and linked to it Assembly order. I can't find any information - how to post the assembly order? The button 'Post' isn't available. When I try to post from the list - it says to me, that the assembly order is linked to the Sales Order.

The Sales Order won't post with message 'There's nothing to Post'. With the debugger I found out that it has linked Assembly Orders. So, I'm missing some steps in this flow.

Thanks