BMO will have sent you a link via email. This link will have information on how to get the discount, as well as a link that you must use when logging into TurboTax Online.
This did not resolve my issue.
I created turbo tax account sometime ago but I received the BMO Turbo tax discount.
Here is the fix.
I am a BMO customer and I also went through the link and didn't get my discount. Here is what I did to get my discount.
Complete your tax return to the best of your ability.
Log out of Turbo Tax.
Go through the portal of BMO for your discount.
When you are on the opening page of your account, click make a copy of your previous completed return.
Open the copy and navigate to the pay page. The discount should now appear.