Charts in Excel or Word are not officially supported in our data template functionality.
We are aware of some customers having success generating basic charts within their data templates; however, this is very much on a case-by-case basis. If you have issues trying to generate charts in your templates, we cannot provide you with any assistance.
Please also realize that even if charts may work currently for your specific case, your templates are not guaranteed to continue working into the future. Should a chart stop working, again we cannot offer any assistance.
Given the lack of official support, we recommend against trying to use charts in your Excel/Word data templates.
In terms of generating charts more consistently, one option is to use our Google Spreadsheets connector to populate a Sheet and then create a separate Sheet with charts that runs off of the connector-generated Sheet.
You can also consider dashboard and reporting tools such as Klipfolio and Zoho Reports - often the easiest way to drive these tools is to use a Google Sheet as the data source for the charts.
Finally, if you run SQL Server Reporting Services or other similar business intelligence tools, you can consider using our Sync product. Sync effectively replicates Form data into a local SQL database running on your servers. This allows you to create and run reports locally using your tools of choice.