I did not use enough sugar, my error was not understanding that the temperature to enter in the calculator was the highest during fermentation, I based it on the temperature, post cold crash, at time of bottling.Beware oxidation. Did you not use enough priming sugar? If that's the case, I'd get them cold, open each and dose with the proper amount of sugar to compensate and re-cap.
If you used enough sugar, the seals are bad. Same remedy, just need better seals.