You need to make sure that you have the latest and correct version of the new launcher which was updated again about and hour ago, so go and make sure that you are on the correct version!

Okay, this seems to be the most common error players seem to get so I will go over it first. This is an error stating that the modpack Attack of the B-Team was unable to install or something along the lines of that. It will also give you a long message reading off the Mod specifically that wasn't able to install. Below will be the instructions you will need to fallow to resolve this issue and resume your well wanted Mod Pack. So lets get started.
Step 1: You will need to go ahead and close out of the error message but keep the launcher open!
Step 2: Navigate to the Attack of the B-Team Mod Pack and press Play
Step 3: The installation should resume from the where you left off but starting with the mod that had the error last, if you get the error message again (very likely) then just repeat those steps until it installs the mod. It will eventually install, please just have patients seeing that this being the largest pack on Technic Launcher it will take some time. But in the long run it WILL be worth the long hard fought wait.
Step 4:After you have gotten past the stubborn mod that didn't want to install,you may re-encounter the same problem but this time with a new mod. Don't worry, just repeat the steps again and keep doing so for every mod that does the same!