java.lang.NoSuchMethodError: net.fabricmc.loader.FabricLoader.getGameProvider()Lnet/fabricmc/loader/game/GameProvider;
at me.modmuss50.optifabric.mod.OptifineSetup.getLaunchMinecraftJar(OptifineSetup.java:299)
at me.modmuss50.optifabric.mod.OptifineSetup.getMinecraftJar(OptifineSetup.java:277)
at me.modmuss50.optifabric.mod.OptifineSetup.getRuntime(OptifineSetup.java:84)
at me.modmuss50.optifabric.mod.OptifabricSetup.run(OptifabricSetup.java:41)
at com.chocohead.mm.Plugin$$Lambda$62/904208473.accept(Unknown Source)
at java.util.ArrayList.forEach(ArrayList.java:1249)
at com.chocohead.mm.Plugin.getMixins(Plugin.java:340)
at org.spongepowered.asm.mixin.transformer.PluginHandle.getMixins(PluginHandle.java:128)
at org.spongepowered.asm.mixin.transformer.MixinConfig.postInitialise(MixinConfig.java:796)
at org.spongepowered.asm.mixin.transformer.MixinProcessor.prepareConfigs(MixinProcessor.java:568)
at org.spongepowered.asm.mixin.transformer.MixinProcessor.select(MixinProcessor.java:462)
at org.spongepowered.asm.mixin.transformer.MixinProcessor.checkSelect(MixinProcessor.java:438)
at org.spongepowered.asm.mixin.transformer.MixinProcessor.applyMixins(MixinProcessor.java:290)
at org.spongepowered.asm.mixin.transformer.MixinTransformer.transformClass(MixinTransformer.java:234)
at org.spongepowered.asm.mixin.transformer.MixinTransformer.transformClassBytes(MixinTransformer.java:202)
at net.fabricmc.loader.impl.launch.knot.KnotClassDelegate.getPostMixinClassByteArray(KnotClassDelegate.java:247)
at net.fabricmc.loader.impl.launch.knot.KnotClassDelegate.tryLoadClass(KnotClassDelegate.java:150)
at net.fabricmc.loader.impl.launch.knot.KnotClassLoader.loadClass(KnotClassLoader.java:155)
at java.lang.ClassLoader.loadClass(ClassLoader.java:357)
at java.lang.Class.forName0(Native Method)
at java.lang.Class.forName(Class.java:348)
at net.fabricmc.loader.impl.util.DefaultLanguageAdapter.create(DefaultLanguageAdapter.java:50)
at net.fabricmc.loader.impl.entrypoint.EntrypointStorage$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:47)
at net.fabricmc.loader.impl.entrypoint.EntrypointUtils.invoke(EntrypointUtils.java:35)
at net.fabricmc.loader.impl.launch.knot.Knot.init(Knot.java:157)
at net.fabricmc.loader.impl.launch.knot.Knot.launch(Knot.java:71)
at net.fabricmc.loader.impl.launch.knot.KnotClient.main(KnotClient.java:23)

Full error log please

Can you upload your latest.log from your logs folder?

I suspect you have an old version of OptiFabric that was not compatible with Fabric Loader 0.12 and above.