Access same online Vault from multiple workstation user accounts

My desktop Win 7 Pro,  is used by three family members, each with a windows user login account.   An Identity Safe Vault was created within one of the windows user accounts.  It works fine there and from a laptop.

Now, I wish to let another user on the same PC also be able to open this same Vault.  They have logged into NIS with the same eMail and password account details BUT ID Safe refuses to access the existing online vault.  It keeps wanting to create a new online vault for the other user on this same PC.

So, I don't see why this should be a problem since the Vault is accessible from other PCs.