Please check R3 2016 release notes and the list of changes.
Check the HTML rendered on the page and if HTML elements of TelerikReporting viewers are there. Also check the browser's Console for errors. Debug the code to trace if the button click event is handled correctly.
In order to troubleshoot the problem further, please post details about errors, or open a support ticket and send us the upgraded project in a ZIP file (you can exclude Telerik DLLs to reduce the size of the ZIP).
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