On my localhost site I've set up a couple of plans and have successfully imported all my users into the free plan.
On my live site I've set up the free plan. I've run the import and it says successful but it shows as 0 active subscriptions.
Also the cbsubs_subscriptions table is empty.
The history site doesn't show any updates or inserts to User subscriptions and the error log is clean.
I've looked at one of my test users and in their profile it lists them as a member of the free plan.
Update
Found the reason - had Create Subscriptions also for free lifetime plans: set to No
Thought I'd double checked all the settings between live & test but obviously not!