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williv1's profile

New Member


4 Messages

Monday, October 3rd, 2022 7:02 PM

NumberSynch Error Message

My new Galaxy Watch 5 will not synch with my Z-FOld 3 phone. The error mesasge is:

NumberSynch has encountered a problem. We're sorry for the inconvenience.

Code: SD-SDK-400

None of the technical support representatives know what to do. I have been on the line with AT&T for 4 days. Has anyone else seen this error?

Accepted Solution

Official Solution

Community Support


221.5K Messages

1 year ago

Hi williv1 we're here to help get your Galaxy Watch 5 synching with your phone.


Make sure you have the most recent software for your wearable and the Samsung Galaxy Wear app on your smartphone to ensure you have the latest features and device protection options.


Repeat the steps for setting up NumberSync to synch to your wearable. The following is required to use AT&T NumberSync: 


• An AT&T postpaid wireless account that’s been set up for AT&T HD Voice

• An AT&T HD Voice-compatible smartphone

• A wearable device that supports AT&T NumberSync and has eligible AT&T wireless service 

• An AT&T User (Access) ID associated with the smartphone number


Let us know if this helps, and thank you for contacting the AT&T Community Forums.


Jeff, AT&T Community Specialist

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