The answer to 'why is my GFCI outlet circuit overload' is that the circuit is drawing more current than the GFCI outlet is rated to handle. This can happen if there is a short circuit, ground fault, or too many devices plugged into the circuit. Symptoms may include the GFCI tripping, circuit breaker tripping, or devices not working properly.
To troubleshoot, start by unplugging any devices from the GFCI outlet and resetting it. If it trips again, there may be an issue with the wiring or GFCI itself that requires a professional electrician to inspect. If resetting the GFCI allows it to stay on, the issue is likely due to too many devices drawing too much power. Try unplugging some devices or moving them to a different circuit.