Hi Sandesh,
Thank you for contacting us here at Microsoft Community.
Since the discount is only redeemable for selected exams please select an exam first before claiming the discount.

You may follow this link as a sample on how to claim your free exam.
If the discount is still not kindly follow the troubleshooting steps below to eliminate possible browser issue:
1. Use other browsers.
2. Clear browser cookies and cache or open browser in In Private mode.
3. On the Delete Browsing History window, make sure to uncheck Preserve Favorites website data and check both Temporary Internet Files and Cookies then click Delete.
4. Allow all third party cookies through the browser settings.
5. Please make sure that you have the latest version of the Edge browser or Internet explorer.
6. Make sure that your profile is updated and all field with red asterisk (*) should be filled with information. Please also remove all special characters in the profile information.
Then, send us a copy of a complete steps by step screen recording(PSR) from the trouble shooting steps until the claiming process of your exam.
I also requested additional information to locate and verify your profile. Kindly provide at least three (3) pieces of information to verify your profile.
To view your private message inbox, please click the icon on the top right side of the screen, refer to the picture below:

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.
Regards,