UPDATE: If I use a different laptop (one without JRiver installed) and go to the JRiver panel at
http://my-ip:52199/Panel/it prompts me for a name and password, and if I enter it correctly I get in and can browse the files etc.
But the laptop that has JRiver installed won't connect; my hunch is that the password isn't being accepted since I changed it about a week ago, but I haven't figured out a way to get it to ask for a name/password to log in with the new password.
This seems like a bug - if the name/password is the failure, it should prompt for a new entry, not just try the old one over and over again.
UPDATE 2: Using the same laptop that has JRiver installed, I can also go to the panel website, enter the name/password and browse everyting.
So, the problem appears to be that MC is using the wrong password and I can't figure out a way to get it to use the correct one- if I create a new library with the same access code it still doesn't prompt me for a name and password.
I tried deleting the old library and creating a new one, but since the Access Code is the same it appears to be trying the same name/password instead of prompting for a new one.