Have you contacted Mitsubishi Connect support specifically about this issue? I had a similar issue in the beginning, but after one of the techs did something (changed a setting only they can access) it's been pretty reliable ever since. They also recommended the following:
1. Login To the My Mitsubishi Connect App
2. Click on the Settings icon
3. Once the Account Setting screen appears, please click on the "Manage Vehicles" section
4. On the Manage Vehicles screen, please toggle the setting for "Privacy Mode" until you see the grey section on the right of the switch turn red. You will need to enter your PIN for the setting to be modified and after the option has been enabled, you will receive a notification that "Privacy Mode enabled successfully"
5. Next, turn the privacy mode off. You will slide the button back to the left and you will see the red on the right of the button return to grey. You will receive a notification that "Privacy Mode disabled successfully"
6. Now back out of the Manage Vehicles section using the arrows until you have the icons at the bottom of the screen.
7. Click on the icon that looks like an arrow pointing up to the right, enter your PIN and the location of your vehicle should appear. If you get an error, please note the exact message you receive and reply to this message. Log out of the app completely and log back into the app and try the Car Finder remote operation again.
Keep in mind that since you are communicating the instructions via satellite, if there are any overhead obstructions at the time, it could interfere with being able to find your car at all.