Modpack update does not add new mods

[cgar]

I created a modpack (CGarz Tekkish 2) and decided to add InvTweaks and ForgeEssentials a day later. So I updated the modpack zip, adding the mods and changed the modpack location to the new updated zip and incremented the version. However the mods were not added after updating on the client. This worked last time on my other modpack (CGarz Tekkish) about a year ago.

Has something changed? Why wont it add the new mods?

EDIT: My friend updated and it appears to have added it for him after updating to another version change. It did not add it on the last update though. Very strange.

Edited July 8, 2016 by cgar