My serial nunber is " not recognized" Sleep Buds are less than 6 months old !
How do I know whether the "O" is supposed to be a letter or a number ???????
Pretty sure the 0 is a number. I think they avoid using the letter to prevent confusion.
You will probably find there are 3 serial numbers (at least I found that on by in-ear buds). There will be one on the case which is for the case and then if you use the app, you may see the numbers for the left/right buds.