I'm using RU server 2.6.0.3 and Host/Viewer 6.8.0.1
I found when configuring a host to use
Custom Server Security, the capitalization of the username matters. For example, logging on with username "johndoe" will fail if the username on the server is "JohnDoe". Also, the logon will fail silently, in that after the "signing in" message, no messages or dialogues will show indicating the logon failed. The assumption is that it succeeds but no permissions dialog shows either.
A failed logon from a viewer does say "invalid username or password" as an Address Book Error, but that is a little misleading to the user who may not remember the case sensitivity of their username and think the address book just didn't sync.
If case-sensitivity is by design, more clarity is needed through the documentation and app dialogues to remind users.
My suggestions:
1) Usernames should not be case-sensitive, since typically they are not in Windows.
2) Unsuccessful logons should be prefixed by something more meaningful, eg "RU Server Authorization Failed"