We need to know more about it before we suggest adding more sugar. More sugar usually just results in bottle bombs if the initial sugar you added hasn't been eaten by the yeast.
When you had it in the bottles for the 3 weeks before you moved them, where were they? What temps were they at then? If you had them too cold, cold enough for the yeast to be dormant, then it would be like having just bottled them, and wouldn't really count as carbing time. Therefore that 1 week you might have had them warmer would only be the first week of carbonation and they might simple still need another 1-2 weeks.
Also what was the gravity of the beer? If it's a big beer, it could take 6 or 8 weeks to carb up.
I usually don't recommend folks trying to fix bottling problems until it's been 6 weeks or so in the bottles, because especially if you want to add more sugar, you need to make sure that all the existing sugar really has been consumed.
But rarely unless it's a big beer, does one need to be "fixed" and you have to be very careful just how you would attempt to "fix" it.