You have an unsupported Android device. With Muse Monitor, I have had feedback from a number of people with the LG G6 with this problem and a couple from people with the Samsung Galaxy Tab A. LibMuse also doesn’t work with the Amazon Fire TV, which I have at home, so decided to just not publish it for that device.
Usually it’s the right ear raw data that is NaN, but on some devices I’ve seen intermittent NaN on all RAW EEG channels which would result in you also get NaN on the brain wave channels.
A super annoy thing about this problem is that if a channel only ever gets NaN, the API reports the sensor as having a good connection! This is probably because all the connection states are initialized as good and only change to bad after some data has been analysed… and if it never gets any data, then it just stays as good. This means there are probably a bunch of people out there using the Muse Calm app where the headband is getting NaN and their calm calcs are junk.