Hi Saba Aslam,
Thank you for your sharing.
As you mentioned "It is windows 10", if you are re-enabling Outlook application under Windows 10 Settings > Notifications options, are you getting any changes in behavior?
First, Do not open Outlook.
I am sharing steps about how to find Notifications settings under Windows 10 OS:
In Windows 10, select Start icon > Select Settings (gearicon) > Select the System category > Select Notifications & actions > Scroll down to the Get notifications from these senders section > Turn off the Outlook application toggle button > Restart PC.
Again please go to above provided settings options and Turn on Outlook application toggle button again. Then Open Outlook application and try to check result with test email.
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On the other hand, please try to create one another test Windows 10 user account profile, then try to check if it makes any kind of difference?
Note: in test Windows 10 user account profile, you may need to downloading and installing fresh Office 365 suite from web portal (I have linked official document just for your reference).
Make sure that Outlook application should be enabled according to the above provided steps under Windows 10 Settings in test Windows user account profile.
Note: If you are an End user, you may need to get help from your IT admin department to create a test Windows 10 user account profile and for further test.
Please feel free to let me know your further updates. I will provide you further information based on your next update.
I would really appreciate your most precious time.
Sincerely,
Vaidya Darpan