Dear Humbert,
Thank you for reaching out here at Q&A portal (a lit bit wrong tag but ok). For the AZ-900 exam, the link to take the test is typically sent via email from Microsoft or the exam provider ( in this case it is Pearson VUE ) shortly after scheduling. Check your email inbox (and spam/junk folders) for a message from ******@pearsonvue.com. Log in to your Microsoft Certification Dashboard (https://aka.ms/certdashboard) to find your exam details. If you still can’t locate it, contact Microsoft Certification Support immediately. Phone is provided here Your region’s support number as well chat is available on their support page.
Since your exam is today, act quickly VUE can often resend the link if needed.
Best of luck on your exam!
Alex
P.S. If my answer help to you, please Accept my answer