smbv2 samba sharing between Windows 7 and Android stopped working for MyUser, but it works for admin I used 2 apps that can connect from Android (Nougat)  to PC (Windows 7). Hitherto that worked perfect. Now I get user authentication problem when I try to connect from Android to PC with "username" credentials. But I can connect without issues using administrator.

It tells me that there is a user specific setting that changed. I didnt change anything. What setting is this? Any idea?
If you are using a local user connection go to manage->users and reset the password.
Maybe the user's password is blocked. there is a windows mechanism that if someone tries to connect X times using bad credential the user turned to be blocked.