Hello Vasu,
Let me help you in registering your AI-900 exam.
In scheduling your exam, please make sure that all the required fields marked with an asterisk* are correctly filled (Please remove any Special Characters (like., \! @ # etc.,) from your Name and Address), save & continue.
It will also be helpful to allow all third party cookies through the browser settings and make sure that the browser is updated or download the new Microsoft Edge to confirm if it is due to a browser compatibility.
If issue persist, please provide us with a PSR (Problem Steps Recorder) from the time you have signed in until it shows the service interruption error and attach it via private message along with the information needed to verify your profile.
Please refer to the image below to see this option or click on this link:

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,