Subject Re: [firebird-support] New Firebird 3.0.4 install can't attach, sysdba & password rejected?
Author Carlos H. Cantu
Re: [firebird-support] New Firebird 3.0.4 install can't attach, sysdba & password rejected? Firebird 3 allows users with the same name to exists in different authentication plugins, so you need to be sure that the user/password you are using in the connection really exists and are correct in the authentication plugin being used.

Also, note that:
isql C:\Firebird\<database>.gdb –u sysdba –p <My password> 

In Firebird 3, the above command will connect using an embedded connection. In embedded connection, password is not validated. Try this:

isql localhost:C:\Firebird\<database>.gdb –u sysdba –p <My password>

and see if it works. It will force connection to be done with tcp/ip instead of embedded.

Migration Guide to Firebird 3 eBook

I’ve been developing a Firebird database and application in Delphi for many years; I’m currently using Firebird on my development server. I’m trying to get it to work on a Windows 10 tablet (to test how well it would work) and I’ve installed firebird  server and the program and put the database on the tablet. My problem is that I can’t attach to the server either with database workbench 5.4.4 or my program which uses the latest FireDAC found in Rad Studio 10.2 update 3.
When I attempt to connect to the server I get the message “Username and password are not defined”, when I installed the server I did select the option to allow legacy authentication since I’m not sure that FireDac currently supports the newer authentication that is available in Firebird 3. On the tablet I was able to connect to the database using isql: “isql C:\Firebird\<database>.gdb –u sysdba –p <My password>” so I’m kind of stumped as to why neither my application nor Database Workbench can attach to the database using the correct username and password when legacy authentication has been enabled (I did check the firebird.conf to confirm that).
Any idea’s what the problem is? Some kind of client library issue?