1) Verify the cabling of the IQ Bus current loop connectors one of them may be reversed.
2) In the Communications Setup window make sure the proper settings are selected. If connected with an RS-232 cable to an Interface than the the Local RS-232 should be enabled and the "Use RS-232 Current Loop Converter" and IQ Net Enable should not be Checked.
The Current Loop converter was an alternative choice to an IQ System Interface for a while but is no longer avalable.
The IQ Net option is for when using the IQ Net software. The IQ Net software allows a computer to act as a server for the IQ Current Loop devices over an Ethernet. In this case the server computer would be running IQNet and the remote networked computer would be running the IQ for Windows with the IQ Net option engaged.