[Modpack not launching]

I have actually been using my computer to code in java so the version I have running on here is kind of important, if I can't then that's unfortunate I guess! Thanks anyway

[Modpack not launching]

I have 16Gb of RAM in my pc, running windows 10. 

I attached the snippet of the command prompt after running the java -version command

[Modpack not launching]

The modpack opens on the "default 1.8.0_211 32-bit" version, but the issue is that I need more than 1 gb of RAM to run my modpack and it will only allow me to change the RAM if I choose the "12.0.1 64-bit" version - and when I try and play with the 64 bit version it first gives me a warning that it has issues and then when I hit continue it doesn't open anything and goes back to the technic launcher as if nothing happened - i.e. no error message past the initial warning. 

note: I am running 64bit Java in case that's a question.