Couple of things you can do to troubleshoot Roaming Profile Error 1521.
- Check the permission, may be you don’t have the right permissions on the share.
- Check if you can browse to the correct share and folder on that server.
- Try creating a new user in AD and logon to the users PC and see if the problem goes away. If it doesn’t then see below:
- Rename their existing profile folder on the network “10 characters or more” that will create the profile automatically and fixed the issue and the user is now able to login without any errors.
- Firstly, create a backup of affected profile
- Log on as an Admin and delete the user’s profile from that computer. Delete that and let the user log in back again. See if it works.
- This will delete the profile from the profile directory and from the Registry.
- Go to the registry and browse to HKLM\Software\Microsoft\Windows\CurrentVersion\ProfileList and locate the key that corresponds to the affected User. It will probably be something like S-1-5-21-1448495065-183601144-544252307-9073 (this is the SID of the user) and in the right pane will have the username. Select the SID on the left and delete.
- Ask the User to Logon again and verify if all is OK.
Relevant post may help you – Delete Complete Outlook Profile by Deleting Profile Registry
Note – Don’t delete anything until you are sure you have backups of the user’s data.