Defold recently dropped support of Internet Explorer 11 for HTML5 builds. If you want to run your game on IE11 (but without sounds) then add this code to your engine_template.html right after the <body> tag.
Tested on Defold 1.2.167.
Changelog
2020-04-16 - Added “resume” implementation for AudioContext for Edge ≤18, Chrome <41, Firefox <40 browsers.