The first time I started HWMonitor, it showed like 1 or 2 temps. For some reason it didn't populate the rest of the stuff right away.
I left it open for a few minutes and then closed the program and opened it again and everything was populated like it was supposed to be.
Every time after that, everything showed up correctly.
I don't know if that somehow helps you or not, but maybe it will.
You could try uninstalling, restarting, reinstalling it, and then trying the above steps that I did.
I can't tell you much else other than that.