The original css is copied verbatim into the uniquely named wcct.css (which the tabbed mdx references/links to). Make sure to modify that one instead for it to be picked up by the tabbed mdx. I kept the names unique to avoid collisions. You can paste the contents of css from #661 into that css (overwrite the existing css of course)
Look for “/START dictionary specific CSS/” to paste over. Do not delete the lines above this marker.
The original MDD can be reused without any modification or repackaging.
But the mdd which I can find contains mp3 files like so: <a href="mdx://mdict.cn/sound/5188089/en/Atalina/take.mp3">US</a>
Therefore the problem is mismatched data format (apparently there are two totally different mdd+mdx combos, one for mp3, another for ogg audio formats)
My guess is that the possible causes are
mismatched mdd - audio file format
ogg file not supported by operating system or browser engine.
Your explanation makes total sense for me. It’s probably that my MDD does not match the MDX. I’ll try those two files you shared again with your modified CSS.