When trying to access from new server to old shares you might get this 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”.
you need to allow insecure guest logon :
Or through group policy:
Navigated to Computer Configuration -> Administrative Templates -> Network -> Lanman Workstation and selected the Enable insecure guest logons as shown in the below screenshot