I get the exact same error attempting to complete my mother's 2020 taxes. She only has 7 T-slips. This is something new with TT2020 since I have used this feature for several years. The message received is
You don't have permission to access "http://test.turbotax.intuit.ca/product/services/tdis/index.jsp?" on this server.
Reference #18.ee[phone number removed]889.516272bb
After 75 minutes with Intuit Tech Support, the solution was
"Enter the data manually."