There is no app needed to scan a Flowcode! Anyone can scan a Flowcode using just the camera on their smartphone. Aim your camera at the code and tap the notification banner when it appears (this step is not necessary for newer phones). If you are farther away from the code, you may need to zoom in a bit to focus on the code.
If the code does not scan when you hover your phone over it, it might be due to the type of phone you're using. If you have a Samsung device, try holding down the home button. A talking bar should appear, and to the left is a QR code icon. Press this icon and Google lens will appear and scan the code. If your phone does not have Google lens activated, open the quick settings panel and enable QR code scanning. Now, you should be able to scan the Flowcode.