I believe it has to do with TACACS being enabled, As it is blocking login's using local accounts.  In ours we have an LDAP group configured via TACACS that allows logins.
I have a cisco MDS 9710 switch with TACACS enabled. I am unable to logon using the admin account. Getting access denied. Tried resetting the password for the account but even then logon doesn't work.  Could someone point out what is wrong.
Unable to logon using admin account on a cisco mds switch