It seems like there's an unconnected pin (SW3:P1) in your circuit. This implies that switch SW3 is not properly connected. To fix this issue, you need to connect it to a specific node of your circuit.

However, finding the right connection requires understanding the purpose of SW3 in your circuit. If, for instance, SW3 is intended as a power on/off switch, you might want to connect it in series with the battery.

Since I don't know the specific purpose of SW3 in your project, I'll make a general assumption that it should connect to your battery and one of your resistors. Please adjust this if it doesn't suit your actual requirement. Following these assumptions, you can make the following connections:

Remember to revise these connections if they don't meet your specific design needs.

In Flux, you can make this connection by selecting the wire tool, clicking on the SW3:P1 pin, and dragging the wire to the desired connection point (BAT1:POSITIVE). Do the same for the other connection (SW3:P2 to R3:P1). After making these connections, you should be able to run your simulation.

According to the provided schematic, Yes, SW3 is connected via its pin P1 to the NEGATIVE pin of BAT1. The connection is a part of net 90ffd7997e92765372f991541a6152b9.