I got a new computer and I wanted to install Minecraft (Original version). When I opened the launcher, it shows small message box, writing 'Downloading runtime'. When this download finished, It shows up one more box, and there was written 'Unable to start launcher, please try again.' I tried it almost 20 times and it still isn't working.
I had the same problem so here's what I did.
go to https://minecraft.net/download and where it says "Minecraft for Windows" click on "show more platforms" and try the old download. It worked just fine for me.
Try the following solutions:
- Disable any active antivirus software or firewall (then start the application)
- Update Java by uninstalling current java and re-installing updated java
- Uninstall the Minecraft application and re-install it
- Reboot your computer and attempt to open up the application
If all fails refer to the post by Mojang Support.