I cannot download Bodymovin plugin and come across with this error popup

It looks like you're trying to import the extension into AE. You have to install it with AE closed, then it will show up under Window > Extensions > Bodymovin. 
Install the aescripts ZXP/UXP installer, then double-click the Bodymovin ZXP, which should open the installer and get you going. Then, relaunch AE and you'll see the extension.

You don't import those files, you install them outside of AE. Refer to the instructions on the Bodymovin' site.

Mylenium