Some of you have been having problems installing JAR files. For example you installed Java but when you try to open the JAR installer for OptiFine or Iris Shader or Forge or Fabric, it simple does not work.
I have created a tutorial video on YouTube on how to fix this issue.
Just check out this video - https://youtu.be/nfDtGZo1T-c
Any issues, just post in the video's comments section on YouTube.