With the FBX SDK upgrade in Mixamo from 2014.x to 2019.1, the output FBX file format was also upgraded from 7.4 to 7.5.
Some users with older tools reported compatibility issues or the inability to import the new FBX files. As a remedy, we have added a compatibility option to enable exporting the previous FBX file version 7.4. This option is available in the download format pulldown menu.
This upgrade means you can seamlessly export and upload the latest FBX file versions or earlier. And if your character uses Physically Based Rendering (PBR) materials, those materials will also be passed through seamlessly (although they will not display in Mixamo).
As of Monday, September 28th 2020, Fuse uploads to Mixamo will no longer be supported as part of Fuse being end-of-lifed.