Sadly, the 'Classic' Autodesk Toolbox, with Explorer, Converter and Viewer cannot grok some 'recent' FBX files. Either 'Invalid File' or 'Insufficient Parameters'. {Sulk.}

May be an artifact of the exporting program, may simply be 'Not Forward Compatible'... {Double Sulk}

The more-recent 'FBX Review' can usually read such files, but lacks save/export tools. As a 'wild card' you could try M$ Paint 3D, as its save rig may differ from that loaded. AC Gessler's nimble Open 3D Model viewer has the tools, but seems to have part-migrated to GitHub, got stuck...

ps: I've been getting VP freebies etc for many years, I like your style.