In the last versions of the Google Chrome browser, the Unity Web Player is blocked by default (and extinguished in near future).
In the meanwhile, it is possible to reactivate following these steps (extracted from this Unity Blog page)
Step 1: In Chrome’s address bar, type: chrome://flags/#enable-npapi
Step 2: Find “Enable NPAPI Mac, Windows” in the list, and click “Enable”
Step 3: Hit the “Relaunch Now” button at the bottom of the page