Bitdefender Family Pack 2020 only allows 15 devices as opposed to Family Packs until 2019 which allows unlimited devices. It’s unclear if current Family Pack users would be rolled over to new device limits (which doesn’t seem likely as when you were activating/stacking previous licenses, you were agreeing to old EULA which allows unlimited devices), but those who relied on unlimited device limits may have to search for an alternative eventually.
You can check how many devices you currently have Bitdefender on at https://central.bitdefe
https://www.bitdefender