The answer to 'my system upgrade won't turn on' is that there could be several common causes, such as a tripped circuit breaker, faulty wiring, or a problem with the new equipment. The symptoms may include the system not powering on at all or not responding to the thermostat. Potential solutions include checking the circuit breaker, inspecting the wiring for any damage, and ensuring the new components are properly installed and configured.
If you're not comfortable troubleshooting the issue yourself, it's best to call a professional HVAC technician. They have the expertise and tools to diagnose and repair the problem safely and effectively.