G920A Reading Diag Codes Error

Hi, following is what I got...

Checking hash file... OK
Searching Samsung modem... detected COM36
Reading phone info... OK
Model: SM-G920A
AP version: G920AUCS6EQH1
CSC version: G920AATT6EQH1
CP version: G920AUCS6EQH1
Product code: ATT
Phone SN: R38GA03V3ME
Unique number: 0715F7CDFB73093A
Searching Samsung diag port... detected COM35
Reading phone info... OK
CP version: G920AUCS6EQH1
CP build: Aug 10 2017 12:52:36
Reading data from phone... OK
Reading NV data... error (15)

Done with Samsung Tool PRO v.31.0