When using the command /sort on a chest from the Iron Chests mod, the command does not detect the said chest thus failing to sort the chest.

Possibly an upstream mod issue.

If anyone is able to tell mewhich mod the /sort command is from I'd take a look into if any fix on my end is possible.

Edit, found it: https://www.curseforge.com/minecraft/mc-mods/inventory-sorting

Interestingly, opening the chest and manually sorting them (either using Middle Click or pressing P) works just fine.

Seems to be an issue with expanded storage or perhaps a mixin, not sure when I'll get around to looking at this though.

honestly, I don't know why they have this as a command. Sorting with a command instead of a button seems like something that should not be expected of players. If there is a way to disable the command I will do that in the pack.

Interestingly, opening the chest and manually sorting them (either using Middle Click or pressing P) works just fine.

Looks like this command was never implemented all the way.
kyrptonaught/Inventory-Sorter#63