Have you played Minecraft 1.7.10 without Forge? Because if not that is probably why cause I am pretty sure you have to run the version you want to download at least once if you haven't try playing 1.7.10 quitting then installing. Also the latest version of any Forge download can be buggy as shown with a bug at the download screen. This can possibly be fixed by downloading the recommended version of Forge for 1.7.10 I am also assuming you meant 1.7.10 since the Forge version matches up.