Commercial Fixed Wing
Flight Crew Instrument; Flight Crew Air Transport Pilot (ATP); Flight Crew Multiengine
Workload; Situational Awareness; Training / Qualification; Troubleshooting; Communication Breakdown; Human-Machine Interface
Deviation / Discrepancy - Procedural Published Material / Policy
General None Reported / Taken
Environment - Non Weather Related; Human Factors
We setup pre-flight like normal for Runway XX. No takeoff data for Runway YY.   After push off the gate we were assigned Runway YY for departure.  Before starting we got the data from ACARS for Runway YY.  We took our time and entered it in the box. Then briefed the engine out for Runway YY. Since not flying much in the last year I tried to be helpful by entering data on the performance page since I was PF. I took extra caution to confirm the flap setting going to flaps 2 for Runway YY from flaps 1 for Runway XX which was setup in pre-flight and briefed. After starting engines we did flight controls prior to moving since it was a short taxi. Then we completed the before takeoff checklist to the line.  Upon reaching Runway YY we were running the before takeoff checklist below the line when I saw we still had Runway XX selected. After noticing that the tower cleared us for takeoff. The First officer changed the runway and we finished the checklist. After taking the runway when I selected flex there was a pause then an ECAM for thrust not being in the detent.  I looked down trying to adjust thinking it was set and only just slightly out of the detent. Upon realizing something wasn't right by not getting set power went TOGA as FO also called TOGA and continued as per training and AOM.Not flying much during the pandemic. Even taking our time when things got out of sequence trapping one error not realizing there was more to do.  I have been through the training on this exact scenario and thought how could this happen.  Well it was incredibly humbling getting lead down the path and once you realize it it's already happened.  We literally caught the error during the before takeoff checklist and thinking since we trapped the error during the checklist and completed it that we were ready.Flying more.  Any interrupt in the checklist EVEN if you literally trap the error during the checklist start over. Once you trap one error stop and take a minute to regroup then rerun the checklist. Don't think since you fixed it while running the checklist you are done.
We entered Runway XX into the FMS since we had no takeoff data information about Runway YY. Upon push back; ATC suggested Runway YY was preferred for the winds. I sent a request for data through ACARS. As a crew we entered the new data into the performance page and reviewed the engine out departure for Runway YY. The Captain decided to start both engines and preform the before takeoff checklist to the line prior to taxi so that I would not be task saturated on the short taxi out. As we proceeded to taxi and complete the checklist below the line; the Captain saw that the correct runway was not in the FMS. I corrected the runway and we continued to finish the checklist. When cleared for takeoff the Captain set the thrust levers in the flex detent; we received an ECAM stating the thrust was not in the detent. The Captain; as well as I thought that possibly the levers were not properly placed in the detent. When I realized something was not quite right I called for TOGA and the Captain immediately pushed the thrust to TOGA.After being off for almost a year myself and the Captain not flying much on reserve as well as taking leaves was a large factor. Though we caught one error with the checklist we did not follow through and catch the other. I have had this very scenario in my first simulator about 2 years ago and still fell down the path. We should have restarted the checklist from the top once we saw that there was any incorrect information in the FMS.Follow our training! Try to stay current as best as possible. We worked as a crew and had a good outcome; it would've been an even better one had we just redone the checklist.
Air Carrier flight crew reported they did not follow SOP's for an existing aircraft condition and continued the takeoff.