I understand this specific version is for 1.12.1 but on Curse you say it also works with 1.12 and when launching it, the message saying you need MC version 1.12 or higher appears.
I just ask you remove that it's compatible with 1.12 if it isn't.
Screenshot of Curse:

Screenshot in-game:

This was fixed in 2.0.0.424, sorry for not marking that build as a full release.