This error will be displayed if the camera is not enabled in the app. SWRemote will ask you if you will allow the camera to be used within the app upon launching the app the first time on the device. If you did not enable this function, you can re-enable it in the Settings menu.
Click on the settings App.
Scroll down until you see SWRemote on the left side of the Settings main menu.
Tap on SWRemote.
Enable the camera by toggling the switch to green as shown here:
This should now enable the camera to be used for scanning.