Why does my Cinema 4D License say 14 days remaining when I have a full licence?

Most likely this refers to how long before Cinema 4D needs to check in with our servers to validate the license aka Online Sync Due. It does not mean your license will expire in 14 days. This means you can have 14 days of use, without connection to the internet. 

The dates located to the right of the clock icon refer to the amount of time remaining before C4D needs to check-in or "sync" with our servers to validate the license; the "Online Sync Due" date. This is nothing you need to worry about unless your machine goes offline, because every time you launch C4D or open the Cinema 4D License Manager, the clock resets to the 14-day allowed offline limit. Only when you go offline, the 14 days will start counting down. This is a security measure, so if you do happen to go offline, you are not immediately thrown off and have 14 days to reconnect. I should also mention that if for some reason the 14 days is counting down, you will start getting notifications days before there is no more time left.

Here is an example to make this more clear:
The date shown is 09/12/2020, and if this machine were to go offline, it would have 14 days to gain an internet connection and sync up with our servers to validate the license. So, if my machine “AtomicSamurai” goes offline; it would need to connect to the internet and check-in by 09/26/2020.

Inside Cinema 4D > Help > Licence Manager - S22 and onwards;

Inside Cinema 4D - Cinema 4D R21 -