I have been playing Minecraft Forge (version 1.7.10) without a problem for years until now. When I try to play the latest release, I have no problem. When I try to play Forge, I get this error message saying "sorry unable to start minecraft". (I was playing it just a few days ago!) I have tried reinstalling the launcher, turning off my firewall, restarting my computer, updating java and none of these things work. I have tried everything that is suggested online, but nothing works. I have also tried launching the game on another device to try and isolate the problem, and forge doesn't even appear as a playable option. It is non-existent. How can I fix this problem? Any help would be appreciated. Thank you. 

In general, we don't provide support for any version other than the current latest or LTS. However, I am curious whether this is a user problem or an actual issue with Forge, so I will keep this open until that is determined. Please provide your launcher_log.txt file and the debug.log in the logs folder. If the debug.log isn't present and the launcher disappears before starting, you may need to enable logs in the launcher itself and copy and paste them.

The problem seems to have fixed itself. I tried launching forge a couple of days ago and it works perfectly now. Kind of a mystery to me as I don't know what went wrong in the first place. I will however keep this advice in mind in case this problem happens again. Thanks for your help.