Welcome to the Atlassian Community!
I'm afraid there's probably no easy fix. You have not explained what you are seeing, so we're going to have to answer from scratch ("can't log in" could be "we do everything right, but it says no", through "error message when visiting site", to "there's a penguin asleep on my keyboard")
You will need to debug -
First, question the "restore" - what exactly did you restore? The database? The service installation? Or did you create a new service and point it at the old database? If you did that, did you re-do all the customisations (including any you did to the user directories)
is the service running on the server? Can you reach it in your browser? Do you get a login screen or an error? If you get the login screen, and you put in known-good credentials, what sort of error do you get - a "nope can't authenticate", or something else?
Next step is to start reading logs. Look for problems starting up, or, most importantly, errors in logging in or user directories.
You must be a registered user to add a comment. If you've already registered, sign in. Otherwise, register and sign in.