MonoGame Pipeline Tool generates no output

MonoGame 3.7.1, with Windows 10 x64.

Trying to build my .mgcb file, but the Build and Rebuild commands do nothing and provide no output.
Is there a log file somewhere that might contain more clues?

Where are you running it?

In VS2017 you can go to options->MSBUild and turn on diagnose output (or something like that) and it will print out more detailed information in the output window - maybe it helps