Heroku不显示本地显示的图标

I have an Icon that is meant to clear the search field by clicking it. It works and has been working both in production on Heroku and in test locally. Heroku quit displaying the Icon in production, now only displaying alternative text which means that Icon could not be loaded. It still displays fine locally. I don't know what changed to cause this and I cannot find a fix. Any advice much appreciated.I have an Icon that is meant to clear the searc