It depends on your device. Some cameras might not support this function of scanning QR codes. You might want to switch to another device and see if that works.
Hello Joshua - Welcome to the forum.
Your Android camera may not be compatible with the App Inventor Scanner, but might be compatible with a different one.
Another, from renown extension developer vknow360:
Your Android version?
And Send Your AIA
Why are you requesting this info Alireza? We already have the relevant Blocks.
Because any setting may have changed
hello everyone, thanks for the reply. I found the problem why my scanner wont work, it is because I checked the BarcodeScanner1's Properties called UseExternalScanner. anyways thanks for all the help! <3