You did not enable teh checkbox at the top right corner on your screenshots?
Do it!
"Enable addons of other client versions" -> Was known as "Enable out of date addons".
If you enable the checkbox the addons will load ingame.
If you just change the files it will be overwritten the next time you update the files offically again. So if someone forgot to change the files themselves you got the same problem again.
One addition:
Logout first! Then at the character selection screen select "AddOns" and enable the checkbox THERE.
Someone reported it won't work if you just do it ingame, but will if done at char selection screen.
A hint:
Install the addon "
Votans Addon List". It will help you automatically enable libraries and dependencies of addons. So if you enable this addon, and then enable the addonw hich needs LibAddonMenu-2.0, it will automatically enable LibAddonMenu-2.0 for you too.