Are you getting the error:-
You can't access this shared folder because your organization's security policies block unauthenticated guest access.
These polices help to protect you PC from unsafe or malicious devices on the network
The reason for this, is that Microsoft have increased their security withing windows 10 to block virus issues from ransomeware attacks which is a good thing.
However, you may have lost connection to some shares that you want back. Here is how you do it:-
Press the windows key (on the keyboard) and the letter R - this brings up the Run Command Window
In the box to the right of Open, type:- gpedit.msc
this will launch the group policy editor on this machine
Click on Computer Configuration (highlighted in yellow)
Click on Administrative Templates
Click on Network
Click on Lanman Workstation
Double click on Enable insecure guest logons
Click on Enable and then Click Apply
No need to reboot, you will now be able to access those shares that would not connect.