[Update 2021-08-06]
After verification, it is finally confirmed that the influencing factor is the operating system version, which needs to be upgraded to Big Sur before it can be installed normally. No matter it is packaged directly or re-signed by others, it is necessary to operate on the latest operating system to solve the problem.
IOS15 enterprise packages may encounter a warning as shown below:
XXX needs to be updated
App developers need to update the App to work properly on this iOS version.
The solution
Building enterprise packages using Xcode12.4 or later solves this problem.
