Cannot access CF8 admin

Recently we changed ISPs and I need to access the CF admin to update the external IP to relay email properly. This has never been a problem in the past, we've done it many times. Now, it will not accept our password. I've tried to reset the password as everywhere suggests by editing the neo-security.xml file to admin.security.enabled, value=false, but no improvement. I've also attempted to modify the password.properties file manually, but every time I restart the CF App server, the file reverts back to encrypted=true and appears to generate a new password. How can I force a reset to go through?