The answer to 'my panel upgrade won't turn on' is that there could be several common causes, such as a tripped circuit breaker, a problem with the new panel installation, or an issue with the electrical supply. Symptoms may include the panel being completely dark or some lights/outlets not working.
First, check the circuit breakers in the new panel to see if any have tripped. If so, reset the breaker. If it trips again, there may be a short circuit or overload issue that needs to be addressed by a professional electrician. If the breakers are all on but the panel is still not powered, the problem could be with the wiring connections or the panel itself. This is not a DIY repair, and you should call a licensed electrician to inspect and diagnose the issue.