This video has no sound

Yes. We opened a ticket for the problem, and Microsoft was able to provide a resolution for us. I don't know whether they did something to apply just to our tenant or might apply for all.

As part of the solution, we were asked to re-upload the videos after they made some change somewhere. (Meaning when I opened this thread back in in May 2023, re-uploading or uploading to different places never helped. But after they made a change and asked us to re-upload, the audio definitely did start working. For some videos, the only copies we had were in SharePoint, so downloading then re-uploading did also work.)

I don't know if that will be helpful or not - I was reluctant to update the thread since I didn't know if it was a fix just for us or more globally. I'd suggest you try a few files and see if re-upload helps. If not, then open a ticket for sure.