First of all,
When I launched Minecraft 1.12.2 I clicked the play button, and it didn't work, then I clicked all the buttons which still didn't work. So then I just closed the game and launcher and re-opened the launcher then I logged out and logged back in. At the moment I logged back in I re-launched Minecraft 1.12.2, So then I clicked the buttons and still, the same thing happened again.
This has never happened to me since I first played Minecraft So I don't know why this is happening to me.
If Anyone knows how to fix this, Please comment on how to fix it.

Thank You!