I have what appears to be a functioning YAMon installation, but at least one device, the Xbox One in my living room, does not accumulate upload/download data. The entry in users.js appears to be correct, at least as far as the MAC and IP addresses are concerned.
I have YAMon installed on a Linksys WRT1900AC running LEDE ver 4.4.92. All went well in the installation except for some recurring "sh: write error: Function not implemented " messages on the console which are apparently not significant (mentioning here in case they actually are). There is also a recurring message in the YAMon log: " !!! No matching entry in _currentUsers for 00:01:xx:xx:xx:xx/ xx.xx.xx.xx (xx.xx.xx.xx)?!? - adding 2584 to unknown mac". The obfuscated addresses are the correct WAN IP but incorrect MAC of my cable modem (could be that I changed the cable modem after installing YAMon).
I haven't tried anything yet. I'm thinking that removing the users.js entry and letting YAM rediscover the device might work.
Update: removing the device from users.js did not fix the problem.
Were you able to make any progress on this? I suspect devices located on interfaces other than "br-lan" are not being fully tracked, as I am seeing approximately 20% less traffic (according to ISP) on days when usage is high on non-"br-lan" interfaces.
EDIT: You definitely want to make sure your lan interface is in bridged mode, or you need to edit one of the .sh files (I think I saw the reference for 'br-lan' in yamon*.sh) to account for your lan's correct iface name. When my lan iface was named 'eth0.xx', I didn't see any data on the "Measured at Router" line.
I am now investigating whether the issue is caused by leaving YAMon open in a browser tab. I edited the util*.js script so that the refresh timer automatically stops/resumes when the tab loses/gains focus.
@jay343, I would make sure you don't have an IP address reservation conflict. During testing, one my machines received an address other then the one that was reserved for it. That seemed to piss off YAMon a bit (having two entries for the same MAC address, the MAC on the "new" entry was something like, "UN:KN:0W:N ...."). IIRC, there is a setting that allows you to enable multiple IP addresses per MAC, but I haven't messed with that yet (don't have a reason to).