The problems that Google Chrome users would have experienced when accessing Tutorial transcriptions or IMCO files in SOURCE were caused by an update that was introduced in Chrome.
In their recent releases they disabled NPAPI plugins by default. This removes support for Sibelius Scorch, but it can be re-enabled very simply. The procedure is described here:
The steps are as follows:
Copy this url into the address line : chrome://flags/#enable-npapi and go to the page
Locate the ‘Enable NPAPI’ line, and click on ‘Enable’
Click “Relaunch Now” at the bottom of the screen. Note: Closing and reopening Chrome is not sufficient, you must click the “Relaunch Now” button.
This is a temporary solution. Chrome are apparently about to introduce a new support for plugins.