Making Sure that the App Is Properly Signed
You have to ensure that the app is using the latest code signature format. You can retrieve the signing certificate information from the application's .app file with codesign. Codesign is used to create, check, and display code signatures, as well as inquire into the dynamic status of signed code in the system.
After you get the application's IPA file, re-save it as a ZIP file and decompress the ZIP file. Navigate to the Payload directory, where the application's .app file will be.
Execute the following
codesign command to display the signing information:
$ codesign -dvvv YOURAPP.app
Format=app bundle with Mach-O universal (armv7 arm64)
CodeDirectory v=20200 size=154808 flags=0x0(none) hashes=4830+5 location=embedded
Hash type=sha256 size=32
Authority=iPhone Distribution: Example Ltd
Authority=Apple Worldwide Developer Relations Certification Authority
Authority=Apple Root CA
Signed Time=4 Aug 2017, 12:42:52
Sealed Resources version=2 rules=12 files=1410
Internal requirements count=1 size=176
There are various ways to distribute your app as described at the Apple documentation, which include using the App Store or via Apple Business Manager for custom or in-house distribution. In case of an in-house distribution scheme, make sure that no ad hoc certificates are used when the app is signed for distribution.