Ensure you're not trying to give the user a subscription using your plan as well. If CBSubs and CB Auto Actions are both trying to control the usergroup assignment then CBSubs will win as it does it after that trigger. You have to use one or the other.
Also note this won't work when giving a subscription to a user from backend as the user store happens after the trigger is fired so user store will override the change in which case just select the usergroup manually during edit.
If your plan is free lifetime ensure free lifetime plans are configured to generate subscriptions within CBSubs > Settings > Global otherwise there's no subscription state to condition off of.
Please also ensure you've latest CB 2.x nightly below and latest CB Auto Actions 6.3.1.
www.joomlapolis.com/downloads/doc_details/640-community-builder-nightly-build