This is because the Debian supplied package is massively old (2.6) and doesn’t work (and shouldn’t have been included IMHO).
If you look at at the browser’s developer console, you’ll probably see errors like:
Uncaught TypeError: Cannot read property 'indexOf' of undefined at draganddrop.js
As per issue Installation issue in Ubuntu 17.04 + Blank screen), use the steps from the official documentation to install Grafana:
http://docs.grafana.org/installation/debian/#apt-repository