Some information

Operating system: Windows 10
Java version: 1.8.0_271
Minecraft version: 1.16.4
Baritone version: Null version
Forge mods (if used): Meteor client

Exception, error or logs

https://gist.github.com/Demon-tk/461e97088254a0fcab8ea35bca97d57f
Couldn't load the schematic. Make sure to use the FULL file name, including the extension (e.g. blah.schematic).

How to reproduce

Issue the command @build [schematic].litematic

Modified settings

Default

Yes, I have ensured that the schematic file is in ~/.minecraft/schematics

I have also tied changing the extension to .schematic from .litematic

it's not supported yet, and fabritone is unsupported as well

If you're still stuck on this, WorldEdit's native file format, .schem, seems to work just fine.