[pkscout]

I deleted the existing db user and created new separate users for each machine

This is just plain wrong!  Every machine must be set (via advancedsettings.xml) to use the same user and password to access the database.  Otherwise, it's not shared, is it ? 

I think you could have separate users on every machine.  As long as each user's permissions are set correctly they will all be able to see the same databases, so the databases would be shared.  Having separate users is certainly more complex, but it does give you a small security advantage in that if one of the accounts is compromised you can just delete or change it without having to go reconfigure all the other machines.