@Soen Meng, Thanks for posting in our Q&A. Based on my checking in my lab, I find I can see devices under "device install status".
In General, devices need to check in for the "Device install status" blade to populate records for the application. Please ensure that the devices in question are currently active and have checked in.
Meanwhile, since the app was targeted to the group, please confirm the user or the device is still in the group.
In addition, please also check the following information:
1, Check if the user is still with the Intune license assigned.
2, Check if the tenant is still active.
3, Check if any issue mentioned under "Service health and message center"
Please check the above information and if there's any update, feel free to let us know.
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