Instead of converting .max files online, export to universal formats that any online converter can handle:
If you cannot find a direct version converter, the most common industry practice is to use an intermediate format. Convert 3ds Max File To Older Version Online
This is a deliberate design choice by Autodesk to encourage upgrades. When a file is saved in a newer version, it may contain scene data, modifiers, or render elements that simply don't exist in the older code base. Instead of converting