The PCN has been served as the parking and loading/unloading on the streets listed on the notice has been suspended under a Temporary Traffic Order. Did you not see the sign and read it ?
These signs always use the symbol for No Waiting, and then text for No Loading, as there is no symbol for this.
So please tell us more, like how long was the car parked there before the PCN was served ? Often, people park their car on-street and leave it there for many days, which is always taking a risk in London due to the frequency of parking suspensions.