Did you change you password the last time you were able to log in?
I always verify that I can login from another putty session while I am still logged in from the session I changed the password from.
Have you tried both web login and ssh login?
I am pretty sure that the web session let me change the password to something I wasn't able to use from ssh, probably because it contained an illegal character (was generated from password manager).
If you can't login from either, this thread Lost password? claims that the reset does not delete the old config, just renames it. I haven't verified, so you may want to get verification before doing the reset, if you really need your config.
The only other possible way I am aware of to get your config is to connect a console cable (you have to have a special USB to 3.3v ttl asych converter) and take the cover off. But that has its risks as well.
This will help you remember to make a backup before making changes in the future.