So annoying, have the same error. I asked the support and they referred me to a Photoshop specialist even if I told them that I have problems with Mixamo. Of course he cannot help me...
Mixamo is not understaffed.. they have no staff. Adobe bought the software.. the software does everything on its own. They have now lost the server and dont know how to fix the problem because they never cared about the users in the first place. It was just another way to make passive income. They have never updated this website in the almost 10 years I have used it. Searching animations is wrong.. Animations are old.. No new characters.. I use Mixamo to import my character I created elsewhere.. rig and add a few animations for Unreal... I know how to do all this in Blender already, but it is a waste of time when I already had the tools to do it instantly. Adobe could have made this website better, but instead they forgot out it for greed.