My Modbus Plus drivers are working fine so why can't I connect Concept to my PLC over Modbus plus?

In most cases if your MB+ drivers test successfully with MBX Demo and the Virtual MBP STAT, and you still can not connect to your PLC with Concept, check the Modicon.INI file and make sure you see a line that reads MBP0=5C under Ports settings.
If you see the MBP0=5D then you need to change it there or change it in the Virtual Configuration to match the Modicon.INI file. You should also make sure the check box is checked in the Virtual driver configuration. Power cycle your PC after making any changes.