We had a case where the crew rejected the take off for a minor thing then vacated, did the Before take off check list again, reset both FDs prior to apply take off power and yet rejected the take off as the FMA was not showing “A/THR” in blue. Now the fact they decide to reject the take off is openned to debate. But only after that incident, I learned that “ At Takeoff, if the thrust levers are set back to idle, the A/THR disengages and cannot be rearmed until the aircraft becomes airbone.” From FCOM - Auto Flight- flight Guidance - Autothrust. I found this information very important and it would have prevented an unnecessary rejected takeoff if the crew was aware of it. But I won’t blame them,I was also unaware of that; I always thaught that by just resetting the FDs was good enough to recover everything, well not really.