If you use Google or Facebook to access Motion Array, you will need to create a new password to log in to the Extension Panel or Plugins for Premiere Pro.
You can create a password here (Reset your password), then try logging into the Plugins again (see Email Login Method):
This may affect the way you log in to motionarray.com (e.g. if you're unable to login to your Motion Array account from motionarray.com by using the Facebook or Google Login after doing this, you may need to try entering your email address instead.)