Take the following steps if your Fargo DTC400 is displaying a mag verify error:
Run a magnetic self test from the printer to eliminate your computer or software
Try different cards
Ensure that the coercivity setting in the driver is set correctly
Run magnetic encoding tests from the Fargo Diagnostic tool
Update the printer’s firmware to the latest on Fargo’s Website
Clean the rollers and mag head with 99% isopropyl alcohol