Hello Megha,
Appreciate you for trying the troubleshooting steps provided to fix the issue.
Please be advised that this message occurs due to several reasons and one of them is incomplete/incorrect profile details such as special characters or symbols like (%+@#).
With this, please try the following workaround:
Use the new MS Edge browser that you can download here.
Make sure to disable the Block all third party cookies function from the browser settings.
Go to Microsoft Certification Dashboard.
Sign in with your Microsoft account and password.
On Your Dashboard, click on click Schedule next exam button to select your exam.
Once selected, go to Edit your certification profile.
Fill out all required fields. (Marked with asterisk *). Note: Make sure that the information in your certification profile is correct specially your address and does not have any special characters as the system will only accept Roman (English)Alphabets.
Click Continue and proceed in registering your exam.
If the steps above did not work, please provide us with the PSR (Problem Steps Recorder) of the incident starting from the sign in page until you reach the error through private message so we can escalate it to our Support team. (please make sure to capture all steps above including the troubleshooting done in the PSR).
Click the image as shown below to access your private message.

I can also update your profile if needed.
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.
Regards,