I've been trying to change the config for 'createaddition-common.toml' to enable the furnace heater. It is apparently set as false as default and I've changed it to true. It still wont recognize the change and it is currently disabled.

I'm having the same issue. I changed the config and the error message disappeared. The heater is working on the blast furnace but as soon as i put down the furnace engine it winds down until it stops. Im not really good at telling the version but the .jar file number is 1.16.5-20220129a.

That's very strange, it worked the last time I tried, however, I don't update the 1.16 versions anymore so if it is a bug I'm not fixing it.

note that the not enabled goggles message still appears if it isn't also enabled on the client, the furnace engine should still run, if not i imagine this might be a bug.
What version are you on?