I noticed from your screen prints that the first two (camera "0" and "1") are different than the other two. If things are working correctly and the camera is not selected properly, the screens shown on cameras "2" and "3" are what I've seen returned. In addition, the first two camera results are square, not rectangles like cameras "2" and "3". So I suspect that some other app is interfering with the PA barcode scanner and the camera numbers for your device are "0" and "1".
[By the way, I found out why I had the issue with the PA scanner not being on when I first entered the scanner app screen. I hadn't set the default to the correct camera value. The slider default is "50", not "0" as my camera demands.]
I assume you can take pictures with the camera on your Android. Check that no other apps are using the camera. One way is to tap Settings, Application Manager, swipe to the All tab and check for any app that might be camera related. Disable any such app temporarily. Then try with PA again.
If that doesn't work, try the recommended apps or some others that are equivalent. You can then work independently of PA and avoid using the barcode scanner built-in to PA. Try scanning with the cursor positioned in an Excel cell. Get that working first, then try scanning in PA again by positioning the cursor in the Input Text box of your PA app. If these apps work but the PA scanner does not, then the problem is most likely with your PA settings or at least PA-related. If they don't, then another app is controlling the camera use and you need to disable it or remove it.
One of these two methods should give you the ability to scan barcodes on a camera.
Just to thought I should update the outcome of my testing.
I tested with other phones and it can show up the camera properly. So I think my camera function has interfered with some other background app behind. For some of the phones, it works randomly for some barcode types so I would say for now I wont want to rely too much on the phone scanner feature.
I found a companion device for bluetooth barcode scanning. I tested it on my app at the input box and it reads well.