I have searched the problem online. Each suggestion is out of date and did not work. When I sign into Minecraft and press Play, the game immediately crashes and a message appears saying:

Java HotSpot(TM) 64-Bit Server VM warning: Using incremental CMS is deprecated and will likely be removed in a future release
Error: Could not find or load main class net.minecraft.launchwrapper.Launch

I play on Minecraft 1.12 and my Minecraft is modded. I removed all the mods and the problem persisted. I use Forge mod loader and when I used a non forge account, the problem still came up. I tried playing online and then offline and both don't work. I have tried switching Java from 8 to 7 and this doesn't work either.