Mod loader: Neoforge v21.1.205
Mod version: Cold Sweat 1.21.1-2.4-b05a

Sorry in advance if the change was documented somewhere, but I can't find anything anywhere in the changelogs or in the source code that would indicate a breaking change toward previous entity_temp jsons.

The log confirms that the entity temp is loaded in both versions.

Example of a file in my datapack : datapack_name\data\zyx\cold_sweat\entity\entity_temp\charmander.json :

{
    "required_mods": [
        "cobblemon"
    ],
    "entity": {
        "entity": [
            "cobblemon:pokemon"
        ],
        "nbt": {
            "Pokemon": {
                "Species": "cobblemon:charmander"
            }
        }
    },
    "temperature": 45.0,
    "units": "c",
    "range": 8.0,
    "affects_self": true
}

Behavior as of 2.4-b04b

Working as expected. Being around a charmander raises your temperature.

Behavior as of 2.4-b05a

Being around a charmander does not change your temperature.

I haven't tried it out yet, but I think I know your issue. The formatting for "entity" is slightly off (the inner "entity" is actually "entities"). Because of that, the JSON interpreter can't find "cobblemon:pokemon" and assumes you didn't define a list of entities.

In the previous version, not specifying a list of entities makes it apply to ALL entities in the game, which happened to work out fine in your case since there was still the NBT check. However in this version, it only applies the config to all entities if you put a "*" in the list of entities.

It was really that simple, small oversight from my part! Thank you so much for your mod and for taking the time to answer!

You're welcome! Happy modding :)