Versions
WorldEdit version: worldedit-forge-mc1.12.2-6.1.10-dist
Platform version: Forge 14.25.3.2838

Describe the bug
//setbiome doesn' work, after execute this command by enter message on chat writed about change biome but nothing happen.

I have a world edit in modpack, maybe it's reason? List of mods:
http://prntscr.com/uiyq94
http://prntscr.com/uiyqzz
http://prntscr.com/uiyrjb
http://prntscr.com/uiyrxu
http://prntscr.com/uiysd9
http://prntscr.com/uiysyy

Old versions are unsupported. iirc the forge version had a bug where setting biomes wouldn't mark the chunk dirty so it wouldn't be saved unless you also change some blocks or otherwise update the chunk.