I have installed a GFI circuit breaker and connected it to a simple circuit--a plug. When I plug anything into the plug, it trips the GFI interrupt. The circuit tests successfully, and works well if I replace that breaker with a non-GFI breaker.
The GFI breaker is set up the same way as a non-GFI model, with the exception that the pigtail is in the grounding bar,
What am I missing?

Gerry Stoner

Ground fault neutral pigtail should go to neutral bar, but should have operated in ground even though it is wrong. Would correct.
The hot from GFI breaker goes to receptacle Hot, The Neutral to the receptacle connects to the other screw on the GFI breaker, If receptacle neutral is on neutral or ground bar, it will trip, equal load must be maintained on protected hot and neutral.