Dear @Consoli, Mark,
Thank you for posting your question in the Microsoft Q&A forum.
Based on my own testing environment, I have encountered the exact same issue, the "Approve" and "Reject" buttons are currently not appearing consistently in the native Outlook mobile app.
The workaround I have found is to use Outlook Web Access (OWA) on the mobile device. You then need to select the option to view the "Desktop Site" within your browser (click "Request Desktop Website"). This forces the mobile browser to load the full desktop version of OWA, which displays the necessary Approve/Reject buttons.
However, since the navigation to switch to the "Desktop Site" varies depending on the browser, could you please let me know which browser and device you are currently using so I can help you locate that setting?
I found that, currently, Microsoft has announced a new feature: Support for approving/rejecting email moderation on Outlook Mobile (iOS/Android) through Actionable Messages. According to the Microsoft 365 Roadmap (ID 492743), this feature is currently in the 'In Development' status Microsoft 365 Roadmap. So, in this case, the best way for the Microsoft product team to promote this issue is for you to submit your suggestion through the official feedback channels. You can post this suggestion to Ideas · Community. Many IT have already done so, and adding your voice (and asking others in your position to upvote it) will significantly increase its visibility to the product team.
Let me know if you have any other questions, I'm still stay here to support.
Looking forward to your response!
If the answer is helpful, please click "Accept Answer" and kindly upvote it. If you have extra questions about this answer, please click "Comment".
Note: Please follow the steps in our documentation to enable e-mail notifications if you want to receive the related email notification for this thread.