Cannot access or reschedule a scheduled GH-600 exam due to a mismatch between the registration email and my sign-in account

I have a GH-600 (Developing in Agentic AI Systems) exam scheduled for June 30, 2026 through Pearson VUE/OnVUE.

The confirmation email was sent to one email address (a Gmail account), but I am unable to sign in with that address to view or reschedule the exam. My active Microsoft Learn account uses a different address (an Outlook account), and when I sign in with it, the scheduled exam does not appear in my certification dashboard.

I would like to know:

1. How can I identify which account my exam is registered under?
2. How can I reschedule (or cancel) the appointment before the deadline without losing my payment?
3. If the exam is tied to the Gmail-based account that I cannot sign into, what is the correct way to recover access?

Any guidance would be appreciated. Thank you.