Last known radar return, was roughly 120NM from closest publically known radar site.
If it had PSR at that range you would get some returns but not for long if descending
For SSR It's likely around 15,000 you would start to lose the ability to "see" any SSR returns
Once again sketchy information
I want to know what altitude for certain was last received on radar.
Was this aircraft ADS-B certainly?