All, we just pushed an update to our online DAE to glTF model converter located at http://cesiumjs.org/convertmodel.html
This should fix several of the issues many of you have previously reported on the forum. When you get a chance, please give it a try with your problematic models and let us know if you run into any issues.
If a model you’ve shared with us previously still doesn’t work, please let me know. Do to the high-volume of forum traffic sometimes things slip through the cracks. If you can’t share your model publicly, you are free to shoot me an email directly with an attachment or link. I can’t promise when it will get fixed, but we’ll definitely keep it around until we address the issue.
Finally, I can’t actually take any of the credit for the converter fixes, so a big thanks to Tom Fili for addressing many of your issues.