I tried to follow the Customer Service link in the Add a Review screen of the Online version, and it doesn't work.

It shouldn't be in there if it isn't operational.

TurboTax claims to be able to accept 10,000 lines of T5008. I had five of these slips, but was not able to upload any of my T slips. My husband's SIN wasn't available to me when we tried to download his T slips. In his CRA My Account, we set me up as a CRA Authorized Representative, and could view his SIN in the list, but T slips still did not download. 

1. I entered a lot of T5008 slips manually.

2. Advised by Assist staff to try uploading them., so I deleted those I had entered.

3. When I found we couldn't upload them, I learned they could be summarized. This advice at the beginning would have saved me hours of entry that resulted in no benefit.