If you encounter an issue where a user changed their password recently and they cannot login to their computer encryption system then do the following actions when logged in as an administrator:

Remove the account first from Filevault using this command:
sudo fdesetup remove -user <UFNET USERNAME>

Re-add the account using this command:
sudo fdesetup add -usertoadd <UFNET USERNAME>

After hitting enter, this is what happens in terminal:

Enter the user name: "TYPE" administrator
Enter the password for user 'administrator':
Enter the password for the added user '<UFNET USERNAME>':