Ios/Windows? Normally a failed installation would be retried a couple of times. Another possibility would be to configure the app assignment as available . So they can try to install the app from the company portal. ANother possibility would be to delete the registry key which controls if the app is installed or not
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\IntuneManagementExtension\Win32Apps\{SID}\{App GUID}
If the exit code is not zero its failed... delete that appguid registry key
