The HTTPS decryption feature cannot run on Apple devices running iOS 13 or Mac OS 10.15 because InterScan Web Security Virtual Appliance (IWSVA) cannot create resigned certificates with a 2048-bit key.
IWSVA root CA for HTTPS decryption is not working on the new MacOS (Catalina) as they have certain requirements to be followed. For more information, refer to the Apple support article: Requirements for trusted certificates in iOS 13 and macOS 10.15.
Trend Micro has released Hot Fix 1879 in order to resolve this issue.
This hot fix saves the new default certificates (CA) (SHA256 / 2048-bit) in "/var/iwss/https/certstore/new_default_ca".
For more detailed information, check the Readme file that will be provided when you request for the Hot Fix 1879 from Trend Micro Technical Support.