java.lang.NoSuchMethodError: net.fabricmc.loader.FabricLoader.getGameProvider()Lnet/fabricmc/loader/game/GameProvider;
at me.modmuss50.optifabric.mod.OptifineSetup.getLaunchMinecraftJar(OptifineSetup.java:275)
at me.modmuss50.optifabric.mod.OptifineSetup.getMinecraftJar(OptifineSetup.java:253)
at me.modmuss50.optifabric.mod.OptifineSetup.getRuntime(OptifineSetup.java:81)
at me.modmuss50.optifabric.mod.OptifabricSetup.run(OptifabricSetup.java:41)
at com.chocohead.mm.Plugin$$Lambda$72/1677207406.accept(Unknown Source)
at java.util.ArrayList.forEach(ArrayList.java:1249)
at com.chocohead.mm.Plugin.getMixins(Plugin.java:340)
at org.spongepowered.asm.mixin.transformer.PluginHandle.getMixins(PluginHandle.java:128)
at org.spongepowered.asm.mixin.transformer.MixinConfig.postInitialise(MixinConfig.java:667)
at org.spongepowered.asm.mixin.transformer.MixinProcessor.prepareConfigs(MixinProcessor.java:542)
at org.spongepowered.asm.mixin.transformer.MixinProcessor.select(MixinProcessor.java:439)
at org.spongepowered.asm.mixin.transformer.MixinProcessor.checkSelect(MixinProcessor.java:415)
at org.spongepowered.asm.mixin.transformer.MixinProcessor.applyMixins(MixinProcessor.java:285)
at org.spongepowered.asm.mixin.transformer.MixinTransformer.transformClass(MixinTransformer.java:208)
at org.spongepowered.asm.mixin.transformer.MixinTransformer.transformClassBytes(MixinTransformer.java:178)
at org.spongepowered.asm.mixin.transformer.FabricMixinTransformerProxy.transformClassBytes(FabricMixinTransformerProxy.java:23)
at net.fabricmc.loader.impl.launch.knot.KnotClassDelegate.getPostMixinClassByteArray(KnotClassDelegate.java:162)
at net.fabricmc.loader.impl.launch.knot.KnotClassLoader.loadClass(KnotClassLoader.java:154)
at java.lang.ClassLoader.loadClass(ClassLoader.java:357)
at java.lang.Class.forName0(Native Method)
at java.lang.Class.forName(Class.java:348)
at net.fabricmc.loader.impl.util.DefaultLanguageAdapter.create(DefaultLanguageAdapter.java:50)
at net.fabricmc.loader.impl.entrypoint.EntrypointStorage$NewEntry.getOrCreate(EntrypointStorage.java:117)
at net.fabricmc.loader.impl.entrypoint.EntrypointContainerImpl.getEntrypoint(EntrypointContainerImpl.java:53)
at net.fabricmc.loader.impl.entrypoint.EntrypointUtils.invoke0(EntrypointUtils.java:46)
at net.fabricmc.loader.impl.entrypoint.EntrypointUtils.invoke(EntrypointUtils.java:34)
at net.fabricmc.loader.impl.launch.knot.Knot.init(Knot.java:156)
at net.fabricmc.loader.impl.launch.knot.Knot.launch(Knot.java:61)
at net.fabricmc.loader.launch.knot.KnotClient.main(KnotClient.java:28)
at me.deftware.client.framework.main.Main.main(Main.java:43)

Which Loader version are you using? This would only happen if you forced OptiFabric to run before Loader 0.5 (or are trying the in dev 0.12)