Actually, you don’t need a “ground”.  What you need is a connection between the bottom of the resistor and the bottom (negative) terminal of the voltage source.  In a simulator this is done by a connection list.  If these two are connected to a water pipe, the top of a Tesla coil, the 220 volt AC power, the top of a Van De Graf generator, or Ben Franklin’s kite, the current in the resistor calculated by the simulator will be the same.

So go back to your simulator and make sure there are connections to TWO DIFFERENT points on the voltage source and to two different points on the resistor.

Remember: resistance is futile!