Had this a few times, you would launch the camera app on the watch and all you would get is a blank screen. It would still take photos but wouldn't show you any preview at all.
Just yesterday this happened and I really wanted the preview so I rebooted both my Apple Watch (on 4.3.1) and my iPhone (on 11.4) and still had the problem.
The fix is actually really, really simple and I think hints at the cause. Simply hit the camera toggle control to select the other camera on the iPhone and the watch will start displaying the footage.. you can then toggle back immediately.
I reason that the Watch for some reason is asking the iPhone for preview from a specific camera and occasionally it can get out of sync with what the phone is set to. Toggling the phone to the other camera allows the Camera app to sync up which camera is in use to the watch... anyhow, the screen toggle seems to fix the issue if you get it.
Just yesterday this happened and I really wanted the preview so I rebooted both my Apple Watch (on 4.3.1) and my iPhone (on 11.4) and still had the problem.
The fix is actually really, really simple and I think hints at the cause. Simply hit the camera toggle control to select the other camera on the iPhone and the watch will start displaying the footage.. you can then toggle back immediately.
I reason that the Watch for some reason is asking the iPhone for preview from a specific camera and occasionally it can get out of sync with what the phone is set to. Toggling the phone to the other camera allows the Camera app to sync up which camera is in use to the watch... anyhow, the screen toggle seems to fix the issue if you get it.