Are you using the correct credentials?  If you have access to the registered email address, you can reset the password as below...

sip.audio: 
Enter the email address for the account admin on this page.

ipDTL & hybrIP: 
Enter the Username or the email address associated with the Username on this page.

Important: Do not enter a sip.audio Username or associated email address on ipDTL's password reset page. Resetting the password via this method will cause SIP registrations to fail for this Username, which in turn could also ban your IP address from our systems!

If you're still having difficulty, contact us via a support ticket.