Hi,
It can take up to 5 business days after the second training day before the discount will show up in your account. You can check right now if the discount is there by starting the process of registering for exam SC-900. You don't have to actually register today, just start the process until you get to the discounts page. If your discount is there, the page will look similar to below:
If your discount doesn't show after 5 business days, please ask a question in the Microsoft Certification forum. They can check and get the discount to show up in your account if needed.
https://trainingsupport.microsoft.com/en-us/newthread?threadtype=Questions&forum=mcp
If the above was useful to you, please click Accept Answer.
Thanks.
-TP