This issue has come up quite a few times at my work.
This is caused by Internet Explorer 11 identifying as Mozilla/Webkit and SSRS identifying it as a non-IE browser and disabling printing. A tip - don't use Chrome/Firefox with a UserAgent spoofer, that will show the printer icon but it won't do anything. Printing does, however, work in IETab.
Try changing your User Agent Compatibility string section to:
<meta http-equiv="X-UA-Compatible" content="IE=10">
Or add the following to your web.config file:
<system.webServer>
<httpProtocol>
<customHeaders>
<clear/>
<add name="X-UA-Compatible" value="IE=10"/>
</customHeaders>
</httpProtocol>
</system.webServer>