Username is in use – the program cannot connect you at this time
Your only option is to click OK which isn’t very helpful. Even after a full system reboot the same thing happens. Note that I use Sage 50 Accounts Plus 2011 (v17) but I’ve had the same thing happen before in Sage 2010, 2007 etc and the principal behind the fix hasn’t changed so give it a try.
After half an hour on the phone to Sage support, there is a very simple solution: