When I create a new Marketing Cloud user in the Admin console (for Analytics or Target, for example), the welcome email they received doesn't indicate what their username/login is, needed for when they try to log in and if they are logging into from a browser other than that the welcome email link r...

This happened to me once, and it turned out the orders were not being properly assigned to the products. Rather the products were not being assigned to the order, although the revenue was correctly assigned.  

I get this error quite often, and have yet to find a Client Care rep who can diagnose or treat this issue. I simply keep trying, and eventually it works.