ADS Momentum Error "Singular Matrix found at Row 4"

when i ran momentum for a lange coupler , it gave an error:

singular matrix at row 4

i have no idea about it, what should i do?

also it gave an warning:

could not create the dataset since no citi files could be found.

thanks.

I sometimes get the 'singular matrix' error in Falstad's simulator. It is a vague message which might have any number of causes. In a real circuit it would not necessarily prevent operation.

I've found I must try numerous tricks to get around this error.

* Avoid placing two capacitors in series. Install a resistor in series with one of the caps.

* Some simulators require at least one ground in a circuit. Make sure all voltage sources have a path to ground.

* Apply a sensible voltage to transistor/ mosfet gates. Example, the simulator may be unhappy if you bias a PNP at a greater voltage than the supply V.

* Make sure you did not connect outputs of multiple digital devices together.

* Make sure you did not mistakenly connect a wire end at the middle of a wire.

* Sometimes it helps to install a high-ohm resistor in any spot which might hang up the simulator.

Thanks, BradtheRad.

I have solved this problem by

1) for permittivity of substrate layers in "create/modified substrate", modified "loss tangent" from zero to nonzero.
2) for layout layers mapped as via, choose model "2D Distributed" instead of "3D Distribute".
3) some slight changes i forgot

and i am nor sure which step make it work.