How can this circuit read a value for amps at 0 volts
Some basic facts of elementary electricity:


Voltage is measured between two points; when mention is made of voltage at some point, that is relative to an implicit reference, the "ground"; which most often (and here) is the negative side of the power supply.
As a first order approximation, there is no voltage across a piece of metal wire, even if some current flows inside it.


Considering these two facts, it is normal that the simulator shows no voltage on any wire connected to the negative pole of the power supply, just as observed.