I can confirm that made no difference for me, the option in the phone app remains disabled regardless of how it is set on the Watch.
I don't even think you can have activity reminders on the phone can you? It makes sense on the Watch, not on the phone that I regularly leave on a desk for hours.
I’ve had this problem from the end of November 2018. It ’s a problem for my spouse too. I have contacted Samsung customer service and professional help. I lost hope on the fix from Samsung.
I have decided to return it to the store.
Hi guys. Reading through the comments it seems to me that the Inactivity Reminder setting can't be active on both the phone and the watch simultaneously if they're synced. As a troubleshooting step I'd suggest disabling the option on the watch to see if it then becomes available on the phone. It may be the case at this stage that you can activate the option on 1 or the other but not both, which makes sense to a degree, therefore if the above suggestion works then you will have to choose where you would prefer to receive the notification, and activate the option on that device accordingly. Apologies for any inconvenience this may cause.
I tried this and nothing happened with either still.... Turned off on phone, nothing, turned off on watch nothing.... Just doesn't work full stop....
The developers have advised us that they've identified the issue and added exception routine code for Inactive Time in the next software update of the Galaxy Watch.
When that update comes your way, can you let us know how it is for you?
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