look at this, please help me, its been 3 days and its still loading
Could be worth clearing your browser cache, I've had this before and clearing the cache generally helps. At the time I also cleared my entire browser history, temp files, and cookies too, however that might not necessarily be required.
I have the same issue and it does seem to be an issue on stadia's side. I can't view them on my App either and the share link is broken too on every device I have at hand. The thumbnail is there though when shared.
Here is one example: https://stadia.google.com/capture/bf7cfc57-2cca-4f35-b1cd-b7ebb154e56e