Hi suraj,
Thank you for contacting the Microsoft Community.
I am aware of how frustrating it would be if your exam had been revoked when taking it. Please know that this is not the experience we want you to have, so please allow me to provide you with more information so I can help you reschedule your exam.
Please be advised that as per checking the online exams with Pearson Vue page, during exam candidates are not allowed to use any electronic devices or any other materials, especially if it is not approved. In your case, since you're not aware of using an external desktop and camera, the proctor assumed that you are cheating and that is the reason as to why the proctor revoked your exam. You may refer to the image shown below for more information on the prohibited materials when taking an exam:

Additionally, during the self-check-in process, the proctor will monitor your identity and will review your room to scan. With this, I highly suggest contacting your exam delivery provider as they are the one who is responsible for supporting assistance with rescheduling since they are the ones who can modify and have visibility for the available slots/dates. Please find their contact information below:
Pearson VUE: https://home.pearsonvue.com/microsoft/contact
If you have already contacted them, kindly share with us the Case ID they provided through the private message I have initiated along with the
requested information to locate and verify your account and so I can proceed with a follow up with them.
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.
Warm regards,