Not sure I understand. Did you create a new blank Garmin Connect account for the new watch, and are you now trying to move the data from one account to the other one? Or are you trying to move the data from the old watch to the new one? Or are you using both watches and sleep data does not sync from one?
In the first case - you do not need to create a new account for a new watch. Continue using the old one, and all data will be there, including sleep
In the second case, not all data from te old watch is copied to the new one. Daily metrics, including the sleep, is usually deleted from the watch when synced to Garmin Connect.
And in the third case, if you use both watches, sleep data comes from the Primary Wearable Device, so if you use one of the watches during the sleep, make sure it is set up as the PWD.
