Hi there, thank you for your question. It seems like this error is caused as the NETFILE access code you entered does not match with what the CRA has in their records.
Please verify your code and try to submit again. Your eight-character Access code is made up of numbers and letters and is located on the right side of your Notice of Assessment for a previous tax year. Please note that NETFILE access code is not mandatory so, although not recommended, you can always submit without the code. Please refer to the below CRA link for more information.
https://www.canada.ca/en/revenue-agency/services/e-services/e-services-individuals/netfile-overview....
