Can't login after restoring a backup

I have developed a website in a staging area. This is Perch 2.8.21. Primary admin has name nharding99 with a password.

I have backed up this website (database, templates, html, css etc) and want to restore this into a new installation.

I create a new installation of perch, v 2.8.26, my primary admin user name as I install this is nharding88 (with a different email address from the one used by nharding99). I can login fine after installation with nharding88.

I then restore my dump file from the development website into the new installation.

I now can't login with nharding88 ("Sorry those details are incorrect" I guess that is expected, I'd imagine that the old login is superceded). I equally can't login with nharding99, when I try there is no error, nothing seems to happen and I am left at the login screen.

I know I'm using the correct password, this still works fine with the original development installation.

Do you have any idea what might be happening?