I haven't been able to get mine to read indoors either but it works fine once properly set up outdoors at the range. It's finicky about how the sun hits the sensors. Unless the sun is directly overhead the shields don't really shade the sensors and that can be a problem on a sunny day. I've found it works best on overcast days without direct sunlight.

I had it at the range earlier this week on a bright sunny day and at first it was working but then it started giving real erratic readings. After I moved to a shady spot it started working properly again.

I have yet to be able to get the app to work on either my kindle fire tablet or android phone. Both keep giving connection errors no matter how many times I unplug the cord or switch ends. I gave up and just write the numbers on paper. That's easy enough to do since I'm shooting from a rest only 12 ft away and the display is big enough to read from that distance. I then enter the info on a spreadsheet when I get home.