I've had this same issue for some time, the only useful solve I've been able to find is to use a different launcher. I've been using this one ( https://www.technicpack.net/download) which is also handy for downloading modpacks without much effort, but it doesn't save the game files to the same location as the regular launcher so no mcedit sadly.
Just select "vanilla" in the modpacks page on the technic launcher, install the pack through the launcher, and select play after it's done downloading.
Janine Lenton
I've had this same issue for some time, the only useful solve I've been able to find is to use a different launcher. I've been using this one ( https://www.technicpack.net/download) which is also handy for downloading modpacks without much effort, but it doesn't save the game files to the same location as the regular launcher so no mcedit sadly.
Just select "vanilla" in the modpacks page on the technic launcher, install the pack through the launcher, and select play after it's done downloading.