There is most likely a problem with the phone's /efs/ss_data
file. I think it's basically a key for decryption of your Wi-Fi passwords and other things in secure storage.
Root is required for this fix.
First we need to confirm it's a problem with secure storage.
Install BuildProp Editor from Play Store
Set
ro.secure.storage=false
Reboot, setup Wi-Fi & reboot again
WiFi should now remember passwords if there was an issue with secure storage.
Now let's fix the secure storage issue since we know what's broken.
Set
ro.secure.storage=true
using BuildProp EditorBackup EFS using TWRP/CWM recovery
Delete
ss_data
in/efs
using ES File Explorer in root modeReboot, setup Wi-Fi and reboot again
Your Wi-Fi passwords should be remembered now on any ROM/kernel, non rooted and without edits to build.props
Tested ON: Samsung Galaxy S6 SM-G920T1 MetroPCS Variant on 5.1.1 build DOJC
Note:
This may work on other devices that require setting ro.secure.storage=false
in build.prop for Wi-Fi to remember passwords. I have seen users with Nexus devices experiencing this issue as well.