A user, Clement2005, successfully converted their MyBB database to Discourse following a guide, but encountered a login issue with their existing username and password. awesomerobot and pfaffman explained that passwords are not migrated during the conversion process. As a workaround, pfaffman suggested using an admin link (http://localhost:4200/session/username/become) to log in, and advised users to reset their passwords by clicking “I forgot my password” once on a real server. Clement2005 thanked the helpers and confirmed the solution.
Okay so I managed to successfully convert my mybb database and load into Discourse following this guide
Then after loading ember/cli and visiting localhsot:4200 I see that all the posts and users were loaded but when I try and login using my username and password associated with my mybb account it denies me access.
Incorrect username, email or password
I’m not exaclty sure why or how to proceed beyond this point.
Any suggestions would be most welcome 
I don’t believe passwords are migrated along with users (someone more familiar with migrations can hopefully chime in to confirm this). Are you able to log in by resetting your password by clicking “I forgot my password” on the login screen?
If it’s a development environment (and you said it was) then you can log in with http://localhost:4200/session/username/become
When you move to a real server, you’ll need to tell all of your users to do the forgot password procedure.
I double-checked the script and it does not import passwords.
Thank you all. And also thank you pfaffman for pointing the admin link out.
Cheers 