The easiest way to fix a dead TPMS sensor is to obtain the ID number of the bad sensor and program (clone) a new sensor with that same ID number. If you do this, there's no need for any software to interact with the car's computer because it already has that ID number stored.
The only time you need a scan tool to interact with the car is when you are replacing a TPMS sensor with a completely new one. A new sensor will have a different sensor ID number, and you need a tool to write that new ID number into the computer.
If they installed a new OEM Mitsubishi TPMS sensor in your car, then their tool must be able to write the new ID directly into the Mirage's computer. Either that, or their tool can put the computer into a "learn" mode and each TPMS sensor could be triggered manually...which would result in the 4 TPMS IDs being stored in the computer this way.
The problem with most aftermarket TPMS tools seems to be this: They never actually test them on a Mirage. They work on other Mitsubishi models (Outlander), so the manufacturer assumes they will work on the Mirage. Unfortunately, they almost never do. There's some quirk that prevents most aftermarket TPMS tools from reading/writing TPMS IDs in the Mirage's computer.
View my fuel log 2015 Mirage ES 1.2 manual: 51.5 mpg (US) ... 21.9 km/L ... 4.6 L/100 km ... 61.8 mpg (Imp)