iredadmin initial login not successful

I just followed the guide to setup iredmail.

then want to login iredamdin via https://localhost/iredadmin , the login prompt is pop, I checked the account in the file iRedMail.tips , in the file , I found the username should be postmaster@my-domain.com , the password is also shown , however , it is not successful to login .

Code:https://www.rosehosting.com/blog/how-to-install-iredmail-on-ubuntu-22-04/Would advise what is the possible cause ?

thanks