On the FDA website, they state that they are pulling authorization because the remaining lots are expired.
This planned move has been discussed by all manufacturers for some time, using it as a 'gripe' for the less than stellar uptake by the populace.
Although I'm glad its going away, I think SP is trying to make more of this move than it is for some reason.
https://www.fda.gov/vaccines-blood-biologics/coronavirus-covid-19-cber-regulated-biologics/janssen-covid-19-vaccine#additional