You can find the contact information in the TurboTax Help article What is the TurboTax phone number?.
However, first you might try clearing your browser's cache and deleting your cookies to see if this helps with the download. See the TurboTax Help articles How to clear your cache and How do I delete cookies? for guidance.
Then, make sure you're only downloading information from one brokerage at a time.
And, if these suggestions aren't helpful, see the following TurboTax Help articles for potential fixes:
