Error code 603 means that you have reached the installation limit, which is 3 per license code.
If you haven't installed it 3 times, For more assistance with this issue, please contact us by phone. To talk to our phone support team, visit https://support.turbotax.intuit.ca/contact/ . After entering some basic info about what you need help with, the page will give you the phone number for the team best suited to help.
Thank you for choosing TurboTax.
