If you can see webcam visuals when you click the camera icon on Sparrow Wallet then most likely your webcam is not good enough to capture the QR codes. And you mentioned it as an old laptop then the webcam resolution will be a lot less and even it's not great in new-gen laptops.

You can add an external webcam if a QR code scan is your primary need just go with the copy-paste method (which I always prefer).