I can't sign in to my account. The page keep returning to the sign-in page. BTW, I have used TurboTax for years!

Please try clearing your web browser's History, including the Cache and Cookies. How to clear my browser cache ? 

If this does not resolve the issue, kindly contact TurboTax Support and an agent will be glad to assist you. To get a direct line to someone who can help, click the following link to the Contact Us page. Then complete the required information. A phone number will appear, along with your incident ID. Call the number. 

This will ensure that an appropriate agent is assigned to your query:
https://support.turbotax.intuit.ca/contact/ 

If the issue persist, please contact our Customer Support line at 1-888-829-8608, they will assist you with this matter.

Thank you for choosing TurboTax.