Follow these solutions in order. Test after each.
After extensive research, we've identified some of the most common causes of Minecraft Error 422 on Mac: Minecraft Error 422 Download For Mac
Look for a .zip file or a standalone .jar file. If the download is an .exe , it will not work natively on Mac without an emulator like Wine or Parallels. Step 2: Install Java (Required) Follow these solutions in order
The mod often crashes if it detects the player using Creative Mode or cheats . How to "Download" for Mac Minecraft Error 422 Download For Mac