This is a common problem. Here is an excerpt from an article in draw.io Helpdesk:
We use something called foreign objects in SVG to allow complex, HTML labels on shapes. All modern browsers including Chrome, Firefox, Safari and Microsoft Edge support this (Internet Explorer 11 and earlier does not).
Link to Helpdesk article: https://desk.draw.io/support/solutions/articles/16000042487-why-does-the-text-of-svg-export-sometimes-not-display-correctly-in-ie-and-some-svg-editors-