If you see this error message then you have tried to run a schematic or a spice netlist in simulation without having added a ground symbol (or a `0` or `GND` ground net in the netlist). To run a schematic or a spice netlist in simulationit **must** have a ground. For more, see: [Tips & Skill > To simulate a schematic, it MUST have a ground] [Tips & Skill > To simulate a schematic, it MUST have a ground]: https://easyeda.com/bbs_view_1393.htm