No option to decouple
I have built a small sub-assembly with a small docking port. I have also added a small docking port to my rocket. During construction in the VAB the ports never snap together but I am able to align the two.
Once I am landed however there is no option to decouple. The only option given is "control from here" on the right click menu.
I seem to be missing a step?
Best Answer
Docking ports can be docked to anything in the VAB, but can only be undocked afterwards. As your docking port doesn't have that option, it seems that it isn't docked at all! There probably is something else holding your ship together, as without a working docking port it would've fallen apart. There are several reasons this could've happened:
Are you sure you placed the docking ports the right way round? It should look like this when docked: 
Are you building a 'loop'? It is impossible for parts to have multiple connections to each other. For example, you can't connect a part to your ship using multiple docking ports in parallel, as that would create a 'loop'.
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Answer 2
Decouplers can decouple when only one side is placed against a non-decoupler node in VAB. However, it must be a node, not a surface.
A decoupler has a back side and the decoupling side(the side that would couple to other decouplers). The backside may be placed anywhere on the craft surface. However the decoupling side must be connected to a node. If you put the decoupling side on a surface instead of on a node, then it will not have a decoupler option.
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