In the future you need to reupload assets again, and also if not done yet i recommend to backup the mixamo store characters and maybe even the animations…
http://blogs.adobe.com/adobecare/2017/05/23/download-assets-from-mixamo
Hope they don’t kill off the entire service as a next step.
Hopefully it’s just a “we don’t want to store all your junk” move and they are not getting rid of the service, it’s a nice source of animations!