done by FRP... 
Welcome to Octoplus Box Samsung software version 2.6.6
-----------------------------------------------------------------------------------
Platform: Samsung Android
Selected port: COM41
Selected model: SM-J510GN
Operation: Reset FRP - UserData
Reset FRP/ Reactivation lock operation for SM-J510GN will delete all
user data on the phone (contacts, pictures and others)!
NOTE: You can reset FRP/ Reactivation without losing user data via
Factory Reset FRP/ Reactivation service.
Connecting to server...
Connecting to server...Ok!
Checking resource files...
Downloading resources...
All necessary resource files have been downloaded successfully.
Please put the phone into Download Mode and connect USB cable.
To put SM-J510GN into Download Mode, You have to perform the
following steps:
1. Reconnect the battery.
2. Press and hold "Volume-" + "Home" + "Power ON" keys.
3. When phone turns on, press "Volume+" key.
Waiting for phone...
Firmware write started.
Writing Custom section...
Custom section has been written successfully.
FRP lock is successfully reseted!
Wait 3-4 min then goto "Menu -> Settings -> Backup and reset" and
make "Factory data reset"
Performed by 2.6.6 Software version.
Welcome to Octoplus Box Samsung software version 2.6.6
-----------------------------------------------------------------------------------
Platform: Samsung Android
Selected port: COM41
Selected model: SM-J510GN
Operation: Reset FRP - UserData
Reset FRP/ Reactivation lock operation for SM-J510GN will delete all
user data on the phone (contacts, pictures and others)!
NOTE: You can reset FRP/ Reactivation without losing user data via
Factory Reset FRP/ Reactivation service.
Connecting to server...
Connecting to server...Ok!
Checking resource files...
Downloading resources...
All necessary resource files have been downloaded successfully.
Please put the phone into Download Mode and connect USB cable.
To put SM-J510GN into Download Mode, You have to perform the
following steps:
1. Reconnect the battery.
2. Press and hold "Volume-" + "Home" + "Power ON" keys.
3. When phone turns on, press "Volume+" key.
Waiting for phone...
Firmware write started.
Writing Custom section...
Custom section has been written successfully.
FRP lock is successfully reseted!
Wait 3-4 min then goto "Menu -> Settings -> Backup and reset" and
make "Factory data reset"
Performed by 2.6.6 Software version.