MS Tower - UDP panel - error message

When running a model whose geometry I have imported from STAAD.Pro I get the following error message:

"Some members specified as legs in td/udp files cannot be allocated to adjacent faces of tower. Load calculations not completed. Possible cause is twist about vertical axis."

I was wondering if the reason is that the legs of the tower must be connected in all cases when modelling the geometry in MSTower? In my model, the headframe is connected to the legs through a transition ring. So the corners of the headframe are not connected directly with the legs of the tower below. Could this be the reason? 

In case that the geometry shown in the picture below can be modeled using MSTower, could you please advise on how to solve this issue?