Some users have reported the issue with Windows 10 not storing Wi-Fi passwords and when they restart their device, they always have to type in the password.
There are couple of methods to fix this issue on Windows 10.
Method 1: Click on Network Icon > Network Settings > Scroll Down click Wi-Fi Settings > Look under Manage known networks ( select your Wi-Fi name and click forget to remove).
Now, click the wireless icon in the Taskbar and connect to your network as would you any other time. Restart your PC and see if it remembers the password.
Method 2: Open Device Manager by typing devmgmt Or Device Manager into the Start Menu Search bar. Under Network Adapters, right-click your adapter, then click Uninstall. Now, you’ll need to restart your PC, and reconnect to your network again (Windows should detect the wireless adapter automatically).