Well, one problem never comes alone
Running version 1.5.6?
With these 2 errors you use shared volume Z I assume.
Second error with Library manager. When you start ncs all modules are loaded correct incl Library Manager? Check the log file.
To store on external drive you can either make a shared volume Z and use that in the Settings for Library or you can connect to the external drive going via network so in Library you have for example when storing on a NAS:
If you do the last one is that working?
I am pretty sure that your original message with path not found is about permissions.
Yes, finally I get all your errors and they are all from username/password is not set.