I have an offline device that doesn’t exist. I migrated from another hub and moved everything over and this one device got moved over twice and shows as offline. The working copy of the device I can exclude/include just fine, but the “offline” device is driving me crazy that I can’t get rid of it. I’ve tried excluding it multiple times in a row and it always shows that 1 device was deleted, but the “offline” device continues to show up. After excluding I also tried to “Remove” the device from the edit menu, but nothing happens. I’m absolutely certain it’s the same device as it’s the first device I added from my other hub and the only one I was messing with at the time.
I’d recommend seeing if you can delete the device using the API Browser+.
Took me a while to figure this out so thought I would reply here for others. I have some water detector sensors that were lost so I didn’t have the device to remove it by activating the uppair mode on the device. The constant notifications were driving me crazy and I couldn’t remove them it appeared. So here’s how to do it. Go to the room where the lost device is. Hit the 3 dots and pick remove. Select the device to remove. A page comes up with instructions to use your device delete mode to remove with a spinning circle where Smartthings is looking for it. This is where I didn’t have patience to WAIT! You have to wait a really long time, then it comes up with another screen about not finding and do you want to force a delete! Hit that and you can finally remove the non existent or duplicate device! Patience is a virtue in this case.
You can also manually delete devices from the ST Advanced Web App, the community developed API Browser+, and the ST CLI.