As Mojang Studios has now added both the Java and Bedrock editions of Minecraft to PC Game Pass and Xbox Game Pass Ultimate with the 2.2.720x update to the launcher, it has caused a few bugs. This tutorial will show you how to download the Java Edition profiles (Mod loaders, OptiFine, etc.) to the new launcher.
Windows[]
First, you need to download the mod/mod loader .jar file, but don't execute the file yet. If you do, a popup will probably show you a message saying "launcher_profiles.json could not be found." To get around this, first go to File Explorer. Then, type "%appdata%" in the address bar on the top. Near the top of the list, you will see a folder called ".minecraft". Open it, and scroll down until you see a file called "launcher_profiles_microsoft_store.json", and then right click, select rename, and call it "launcher_profiles.json". Important! Don't forget the .json at the end or it won't work. Make sure to keep the window open and start setting up the download for your mod/mod loader. When it's finished, go back into the window where .minecraft is open and rename launcher_profiles.json back to launcher_profiles_microsoft_store.json. Now you should be able to play your mods without problem.