Recently the mod has not worked in version 1.12.2, I use it with the chisel and bits mod (Which is also 1.12.2)
The game starts as usual, for about 10 seconds at least. and then this error message pops up
The game crashed whilst initializing game
Error: java.lang.NoClassDefFoundError: net/minecraftforge/common/IRarity
I tried using other versions on 1.12.2 and it would say the same error again.
The mod used to work around February last year, but now all the time it comes up with that crash message
Also yes i removed optifine
if you can fix this thank you so much!

Yes I have used the latest version and here are the versions I used to see if it worked:
1.12.2-forge1.12.2-14.23.5.2838 (latest)
1.12.2-forge1.12.2-14.23.2.2611
1.12.2-forge1.12.2-14.23.5.2768
1.12.2-forge1.12.2-14.23.5.2810
I hope this somehow helps!

Try it

Latest version isn't forge 1.12.2-forge1.12.2-14.23.5.2838;
it's 1.12.2-forge1.12.2-14.23.5.2847

Have you tried the latest version of forge 1.12.2? And can you say
which forge version/s you used?

i just tried using the latest one and it came up with a different error message
The game crashed whilst initializing game
Error: java.lang.NoClassDefFoundError: net/minecraft/client/renderer/EntityRenderer

wait nvm i used a previous version of the mod i just used the latest version and now it works! Thank you so much!

Yep, that first issue was because of old Forge version
Will be fixed anyway in the next version.