Open MiniMeters and click Settings from the bottom right.
Under the Audio Device panel and choose "Default Output Capture" from the Audio Device section.
Default Output Capture attempts to capture all of the audio coming out of the primary output selected from Windows.* If the application you are trying to capture is using a different device it will not be captured.
ASIO: Unfortunately WASAPI is unable to capture audio from any program that uses ASIO as it's audio driver.
This limitation exists because ASIO bypasses Windows's audio system and connects directly to your sound card or USB audio interface. Some alternative ASIO drivers such as FL Studio ASIO, or ASIO4ALL may still work with MiniMeters.
Use of ASIO drivers prevents MiniMeters from capturing audio of that particular application by sending the audio directly to your interface. MiniMetersServer (included with MiniMeters) allows you to route your audio from your DAW or host to MiniMeters circumventing this.