If you are using TurboTax CD/Download, please make sure that your software is fully updated. This FAQ has instructions on how to update TurboTax CD/Download: https://turbotax.community.intuit.ca/community/navigating-turbotax/help/how-do-i-update-turbotax-if-i-have-the-cd-download-edition/00/873477
Please review your NETFILE eligibility here: https://www.canada.ca/en/revenue-agency/services/e-services/e-services-individuals/netfile-overview/eligibility.html
Also, if you entered a NETFILE Access Code (NAC), please double check that it is correct and has all 8 characters. You can also try submitting your return without the NAC. The NAC is optional and not required to file your return.
If you are still unable to resolve 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.