Disclaimer: we don't have a DNS-327L box to do tests on therefore my comments are based on over 20 years experience of IT.
First, what are you using as an SSH server/client? Is it an addon or built into the firmware? If it is an addon where did you get it?
Once we have the answers to those questions we might be able to solve the problem. We use OpenSSH here at work and generate our own security cert/keys.
If you are using PuTTY where did you get it from? It might be a very good idea to ask the people that ported it about how to reset a password, after all they should know.