I've been using the BarcodeURL() example from Marketing Cloud's documentation. Their example seems straightforward however it keeps generating a broken image in the Content Builder preview. When sending it to myself for testing it also renders a broken image in the email. I have also tried with several different types of barcodes using the list from the documentation, to no avail.
Here is the example code I'm using in the email:
<p> <img style="width: 400px; height: 200px" title="barcode" border="0" hspace="0" alt="barcode" src="%%=BarCodeURL("BBY01-397101069285","Code128B", 400, 200, 0)=%%" width="400" height="200"> </p>
This is the broken barcode image in Marketing Cloud Preview:
This is how it renders when the email is test sent to my account: