Hi Sanjay,
Thank you for contacting the Microsoft Community.
I completely understand that resolving the invalid voucher issue you're experiencing will help you register for the AZ-900 exam at its discounted rate. Be untroubled by worries, allow me to assist you with this.
Since you already contacted Pearson VUE, and they confirmed that the voucher is invalid on their system, please send me the voucher details along with the other requested information through the private message I initiated. Once received, I'll collaborate to our support team to thoroughly check this issue.
Additionally, as what @Julian have mentioned, we strongly encourage our candidates to take their exams within the voucher validity period. This ensures that you can take advantage of the discount and avoid any potential issues that may arise from an expired voucher.
Moreover, the Virtual Training Day discount is only valid for 90 days from the start of training, and won't stack with other discounts. (Ex. ESI, Student, CloudSkills Challenge, FTE, etc.) To obtain more details about the MVTD discount, feel comfortable to check out this sticky post, or visit the Microsoft Virtual Training Day event page, where you will find useful details in the FAQ section.
I look forward to your response. Please note that if no response is received after two business days, the case will be closed and locked. After the case is locked, we will no longer be able to respond, even through Private Messages. Thank you.
Best regards,