Both just stoped working and cannot be added to the Sync Module. I deleted another one just to test it and was able to add it back.
Are those brand new batteries. If not, try that first. Initial start up of the cameras, for re-joining, is the heaviest power user, and weak batteries will simply not cut it.
Yes, they are new. Tried everything multiple times.
Nobody can help without all the details, including what actually happens when you try. None of us can probably help anyway, even with that detail, so it sounds like a call to support is in order.
You maybe should not show the DSN Device Serial Number of your cameras, just for security reasons. These are registered with the camera owner, used for tech support and warranty.