The type attribute of the script element is determined by the doctype. HTML5 does not require it.
VS will always complain there is a script error or an invalid character because in this case there is scipt directly in the markup but not in a script tag. You can set the string with the desired template from the server code to avoid this if you like, and you should escape the string properly, as advised in the help article I previously linked: http://docs.telerik.com/devtools/aspnet-ajax/controls/htmlchart/troubleshooting/handle-special-symbols. This is not an actual error, however, but a false positive by the code analysis tool.
In your case, though, there must be some kind of JS error that breaks the chart rendering, or there is an issue with the data source. In either case, that would be something specific to your concrete case.
Anyway, I am attaching here a VB version that works fine. One of the charts uses markup, the other - the VB code. I trust this should help you get started.
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