Google Chrome 42 (and higher) has disabled NPAPI by default, and with it, the Silverlight plug-in (in addition to other plug-ins). With the updated browser, when you visit web pages with Silverlight content, you see a gray area with a puzzle piece display in its place instead. Mouse-over the gray area, and the message This plug-in is not supported accompanies it.

  


A quick and easy work-around exists to restore NPAPI to Google Chrome by default. To make your Silverlight content available, just follow the steps below:
  • Upgrade to Google Chrome 42 (or the latest version up to Chrome 44).  NPAPI is enabled by default in Chrome 41 and earlier. Please note that this option is no longer present in Google Chrome 45 or later.
  • In a Google Chrome window, type or copy/paste this line into the address bar: chrome://flags/#enable-npapi and then click the Enable link under Enable NPAPI Mac, Windows.
         
  • For your change to take effect, click the Relaunch Now button at the base of the page.
         

Once Google Chrome relaunches, the Silverlight content will display once again in the browser window. The plug-ins will still be subject to the previous blocking restrictions you may have encountered with Chrome in the past. You may need to give the plug-ins permission to run even with NPAPI enabled.

Source: https://techhelpkb.com/enable-silverlight-in-google-chrome-42/