1. Please make sure the app is installed from App Store.
Recorder Plus is only available on Apple’s App Store. It should not be installed from any other third-party app store.
When any other third-party App Store distributes the app, they need to modify the app and resign it.
Maybe the app will work for some days when it is distributed by third-party app store, but there is no guarantee how long it may work.
2. If your iPhone/iPad is under control of MDM (Mobile device management), please consult your administrator of MDM to make sure all settings were set properly for the app.
To check whether your device is under control of MDM, please open the “settings” app on your device,
then “general” -> “VPN & Device Management”,
For devices which are not under control of MDM, the shown page should be empty (figure 1).
Figure 1
For devices which are under control of MDM, the shown page should have some installed profile (figure 2)
Figure 2