Unable to display image file in Jupyter markdown cell

This code in a Markdown cell:

<img src="images/grad_summary.png" style="width:600px;height:300px;">

works fine in Jupyter browser, but in VS Code with Python extension it does not render at all, only a blank image box is shown. Both are running in the same conda environment.

This alternate method in a Markdown cell:

![title](images/grad_summary.png)

also works fine in Jupyter browser but does not render in VS Code with Python ext.

I searched stack overflow, there was something close but it did not address this issue. Any insights appreciated.