A319 First Officer reported a rejected takeoff after a runway change due to lack of thrust FMA (Flight Mode Annunciator).

Narrative

I was the PF.Origination and preflight walk around complete. We did not receive a PDC so I called clearance; we were told to expect Runway XXR. There was a tailwind reported in the ATIS so I sent for performance data for XXR with a tailwind. The CA and I completed all preflight duties. Together we completed a route verification; reviewed the PERF page (after the new numbers with a tailwind were input) and all other items on the departure brief. We then completed the Before start checklist. I called for push clearance and was told to expect XXL. The performance data on the release had numbers for XXL. As we pushed I completed the runway change in the FMS. I changed the departure runway; verified the SID and checked the rest of the route. Then I entered v-speeds; flap setting/cg; and flex temp. The CA and I verified the new departure with runway change and PERF changes and briefed the new taxi route. Both engines were started and the load close out brief and after start checklist were completed. The CA taxied to XXL. Before takeoff checklist was completed. We were cleared for takeoff. I was given control of the a/c when lined up on the runway. I allowed the IAE engines to stabilize then advance the thrust levers to the FLEX detent. I did not see an indication in column 1 of the FMA (Flight Mode Annunciator). I removed my hand from the thrust levers. Briefly; I saw; MCT (Maximum Continuous Thrust) then CLIMB displayed. The CA called 80 kts and shortly after rejected. When I looked at the airspeed after the reject we were just below 80kts; I called 60kts and let ATC know we rejected. I estimate the reject was initiated between 100-110 kts. We stopped on the runway; determined it was safe to taxi off the runway and stopped. There was a VENT skin isolation valve ECAM which we completed. We completed after landing flow; taxied to the gate; turned the brake fans on (max temp was around 450 degrees and completed the shutdown checklist after parking.As we taxied back to the gate I noticed my MCDU (Multipurpose Control Display Unit) had the PERF page displayed in green and did not show a flex temp input. It is possible I did not enter the FLEX temp after the change to XXL.After advancing the thrust levers to the FLEX detent with nothing populated in column 1 of the FMA I should have checked the upper ECAM.Fatigue may have been a contributing factor. This flight was scheduled to depart at XA:24 but was delayed until XG:49. The previous duty period was also a red eye and after the rejected t/o I called fatigued. Cause: Long duty day preceded by a red eye. I was for duty for this flight.Multiple changes to the PERF page. Follow up with the runway change checklist in the AOM.