If every time you swipe a credit card into your MagTek credit card reader on a Mac computer, you receive an error stating "Invalid card swipe. Please re-swipe your card.", your reader may not be reading details properly.
Using this guide below, you should be able to set up the card reader the correct way on your Mac allowing you to swipe credit cards.
Set the card reader keyboard type
1) Start out by opening your Mac's System Preferences and selecting Keyboard.
2)You will then want to choose "Change Keyboard Type..."
3) This will bring up the Keyboard Setup Assistant window. Select "Continue".
4) While on the screen below, you will want to press "Z" on your keyboard.
5) This will bring up a window saying the keyboard cannot be identified. You want to select "Skip" here.
6) After you skip the auto detection, it will let you specify the keyboard type. You want to choose "ANSI (United States and others)". Once that is selected, press the "Done" button.
Now your MagTek credit card swiper has been configured to send over the correct character data. You will want to test out your swiper once again to confirm it works!
If you are still receiving the error that your card swipe was invalid, you will need to perform some advanced configuration on your MagTek swiper to reprogram the device. This process requires a Windows computer to run the programming software to send signals to the card swiper. A tutorial on this programming process can be found here: Configuring your MagTek Mini USB card reader for Vantiv (formerly Mercury)