i press play and it says "Unable to load" what do i do?

I press my Minecraft on my computer and when is opens I press play but then a few seconds later a thing pops up and says "Unable to load" and it is the newest one (1.12) after the newest one didn't work I tried 1.11.2 just to check if others worked or not, and none did I tried everything, restarting my computer downloading it and more...please help. (also I'm not sure if my computer is windows or java, I'm pretty sure its windows)