Widebody; Low Wing; 2 Turbojet Eng
Air Traffic Control Fully Certified
Air Traffic Control Time Certified In Pos 1 (yrs) 2.5
Situational Awareness; Distraction; Time Pressure
ATC Issue All Types; Conflict Airborne Conflict; Deviation - Altitude Excursion From Assigned Altitude; Deviation / Discrepancy - Procedural Clearance
Air Traffic Control Issued Advisory / Alert
Procedure; Human Factors
I took over the sector around time XB:19. At XA:48 Aircraft Y issued a climb to reach FL360 by XB:20 and to report level due to traffic. XA:49 Aircraft Y wilco. XA:58 Aircraft X issued at time XB:20 climb to FL350 to reach FL350 by XB:30. XA:59 Aircraft X wilco. XB:21 I get a sector message restriction has not been met by XB:20 by Aircraft Y. Time XB:22 I observe Aircraft X at FL344 and Aircraft Y at FL350 and demand the aircraft. Then send a message to Aircraft Y to confirm altitude. Confirm level FL360. Right after that message went out the Aircraft X sent a message that there is traffic at FL350 at time XB:23. Aircraft X received a TCAS advisory and stated traffic passed 2 NM southeast of us. At time XB:24 Aircraft Y is now level at FL360. When I reached out to Aircraft Y to ask why he was not level he stated they were late in timing due to error they will file a report.ATOP (Advanced Technology and Oceanic Procedures) should not allow these clearances in head on situations. I felt as if I had zero time to fix the situation. These clearances get blown every once in a while and it is only a matter of time before something bad happens.
ZNY Center Controller reported a loss of separation due to an aircraft not climbing as instructed.