Hi Graham,
Greetings
Thank you for posting on Microsoft 365 Community forum.
Regarding your issue, first of all suggest you to make sure that your Android device is updated with latest software since you mentioned you have the latest Outlook version so this could be a configuration issue. Further if you have configure multiple accounts in Outlook app, suggest you to temporary disconnect other accounts and only access your main one account and then observe the issue.
Open Outlook app from Android device > select your account > go to settings > Reset your account > restart Outlook app.
Turn off Outlook notification for couple of hours, after that enable it and check the result.
If still same issue, configure your account in different Android device device to check the behavior or you may configure other user account in your Android device to verify it it’s your device issue or not.
If the issue persists please uninstall the App and install it back and observe the results.
However, for using Outlook on Android device, we have a special dedicated support team for it, which is specializing in handling issues related to Outlook for Android. Therefore, we recommend you that for further assistance please go to Outlook for Android support. When you contact our support team, you won't receive an email or get a call back. But you'll receive a notification when the support team sends you a reply, and can easily communicate with them in the app.
Your kind understanding is highly appreciated.
Kind regards,
Simbarashe