Hi everyone,
Just an update – the fix from @khahina worked for me – thanks so much.
@cavalierlife – I had already tried turning that off and on. When I turned it off, the missing icon returned, but then I had 4 other missing icons. When I turned it back on, the 4 icons returned to normal, but the WooCommerce menu icon disappeared again. It could be a theme issue as @mononox states, but the CSS provided by @khahina has done the trick.
Thanks so much.