Air carrier First Officer reported that they missed an item on their pre-flight checks; resulting in a return to the gate.

Narrative

On Day 0; I reported as the FO for Flight XXXX ZZZZ-ZZZ and began the preflight setup. I was the first one on the flight deck and began running through the initial preflight procedure by obtaining permission to start the APU from operations to cool down the aircraft. The setup was busy with a new departure clearance needing to be obtained with clearance delivery; and we were provided with the wrong flight plan by operations. This led to confusion with the fuel load and added workload for the crew. I mistakenly believed that checking the circuit breakers was a Relief Pilot function because the Relief Pilot completes parts of the preflight procedure such as the security and emergency equipment inspection. As a result; I failed to notice that there were circuit breakers popped on the lower panel behind the FO's seat.As we were pushing back; the CA and I noticed that neither of the iPad chargers were working; which prompted me to check the circuit breakers to see if one had popped. When I looked down at the panel to my right; I discovered that multiple circuit breakers popped. By this time; the tow crew was disconnecting. The CA instructed the Relief Pilot to contact dispatch and patch in maintenance; while I coordinated a return to the gate with ground and operations. The CA then directed me to start both engines in order to taxi back to the gate. Once we were at the gate; maintenance personnel boarded the aircraft and investigated the issue. They found that maintenance had been performed on the right pack the previous night; and the breakers had been pulled during those checks but not reset afterward. Maintenance reset the breakers and reissued a Maintenance Release. After a short delay; the flight was able to depart about 30 minutes late.