Nothing can be done as of now. U/Somebody might have rooted the phone. Rooting voids Knox warranty which inturn disables all app that requires knox framework.
Reverse the root, I.e. unroot the device using SuperSU or similar payload, Although don't expect the warranty to be reversed as well, most modern smartphones have a built in Kernel switch ID that changes once it detects unauthorized Root access and modules. It may bring back your warranty, but don't hope much.
