1. It is usually a good idea to attach an example file here, so that those who decide to devote their time helping are able to see what's going on. Without it, it's mostly impossible to say something helpful.
2. In your case, {'kg*'m^2*'H}/{'A*'s^4} equals to Ohm*V, not V, so you must have made some mistake in your calculations (or in units of your input). You may simply manually put V as units for your specific result, and see that Ohm will be added automatically to supplement the unit.
As I said above, there's nothing more to say given the information you supplied.
С уважением,
Михаил Каганский