I just did some snooping around and found that the test button on some GFCI receptacles will not work if the voltage is too low. P&S specs are for 120v + 10, - 15 percent. So a voltage of 102 is at the bottom of the specs.
Other, cheaper brands may have a higher minimum voltage range.
So, I would first check the voltage at the receptacle under a load. And I would do so with different loads. If the test button won't work with say, a portable heater plugged in it, that would tell me it's the amount of load affecting the receptacle, not the type of load.
If there is a substantial voltage drop, or the voltage is just too low to start with, there is bigger fish to fry than trying to make the receptacle pass inspection.