Can't add MRN to account

[Lokolos]

When I try to add the member record number that my bishop gave me I get a message saying, "Either the MRN and/or Birth Date is not valid or the account already exists." If I assume that the bishop gave me the right member number, how do I go about finding out if there is already an existing account for it (maybe set up by my parents and they forgot, or I forgot) so I can log into that instead of the account I've been trying to add that number to?