Hi Tim
You can set a username/password at initial discovery (and that can use templates), but after that you can modify any device, and it will use its own settings. Note that Telnet authentication is different to SSH authentication. So if you were to discover the device, configure Telnet username + password, and then change the Login Type to SSH, it wouldn't understand, because it doesn't have any SSH authentication settings.
Look for "Modify Telnet settings" and "Modify SSH settings" on the Device Details page. Make sure that they're filled in. You can select a template, or manually type them in here. I would suggest manually typing them in.
Make sure that you've got the right combination of settings for username, password, enable password, etc (some devices need enable passwords, some don't).
Those are supported devices, so I'm pretty sure it's something simple. Otherwise we can start looking at the imccfgbakdm logfiles. They'll give us a bit more detail about what's going on, but they can also be a bit overwhelming. Better to start with the most obvious checks first.