"Error! Unable to start game."

[ARandomUsername]

Whenever I open my launcher and select the forge version I want to play (1.12.2), it just says, "Error! Unable to start game." This is the same with 1.12.2 and 1.7.10. I've tried: Deleting both versions multiple times, restarting and hard shutting down computer, deleting mods, installing different versions of forge 1.12.2 (even the recommended one), and deleting the 1.12.2 forge version folder, but nothing works. I'm able to start vanilla minecraft fine but it won't even launch the game when I try to play with a forge version. Before I couldn't even launch the game it said that a had a something.dat, and made me make a backup of my world. When I did, it just kept loading forever.

 

Subtopic: Can someone tell me how to install a modpack while you're at it? RLCraft Specifically. Can I install it without twitch or technic? Thanks.

Edited September 26, 2019 by ARandomUsername

[ARandomUsername]

Which log?