Hello, thank you for reaching out to Microsoft Q&A.
I'm sorry you're experiencing this problem. I understand how important recovering your account is to you.
Could you please check if you can sign in with your @gmail.com account online without any issues?
- Open an Incognito tab on any web browser
- Go to the link below and sign in with your Microsoft account: https://account.microsoft.com/
If you receive the same error message - "This account doesn't exist", it could be due to one of the following reasons:
- Someone gained unauthorized access to your account and replaced the primary email address (alias).
- Your account was deleted due to inactivity for more than 2 years.
- You may have manually closed the account at some point.
Since you were able to access your account just three days ago, it is likely that someone gained unauthorized access and removed your email address. In this case, I recommend submitting an Account Recovery Form to the Xbox support team. Please include your Gamertag (Xbox profile name associated with your account) in the form to help verify your identity and recover your account.
Recover your Microsoft account
Let me know if you still need more help.