After updating from DSM 6.2 to DSM 7 on my Synology NAS, i was unable to connect to my Shared drives.Every time i tried to access the Disks, the Username Password dialog kept popping up, no matter what combination i’ve put in.

Luckily after reading through the changelogs, i’ve found the problem….

Synology disabled NTLMv1 on DSM 7 and my Windows was trying to access the NAS with it instead of NTLMv2 and so it got rejected.

This is how i fixed it:
open Regedit
Navigate to this key:
HKLM\SYSTEM\CurrentControlSet\Control\Lsa
Change this Value
LmCompatibilityLevel
From 1 to 5
LmCompatibilityLevel = 5

Now try to access the NAS and if it doesn’t work, deactivate and reactivate your Network or reboot your machine.
I didn’t have to do anything after it, as it just instantly worked.

I hope this saves you from countless hours of trial and error and huge headaches