Apple released 2 new macOS Big Sur updates, which are 11.3 and 11.3.1, to enhance and resolve some known issues with the operating system. Customers running Trend Micro Apex One (Mac) who upgrade to macOS Big Sur 11.3 and 11.3.1 may receive the pop-ups "Program Unresponsive" and "Unable to start Apex One (Mac) Security Agent".
Trend Micro is currently investigating this concern and are waiting for updates from Apple. Current workaround is to restart the machine after completing the upgrade to macOS 11.3 or 11.3.1. All agent features are seen to work after performing this.
For users of macOS Big Sur 1.4, refer to this KB article:
Trend Micro Apex One (Mac) and Worry Free Security Agent for MAC compatibility with macOS Big Sur 11.4
In case further assistance is needed, please contact Trend Micro Technical Support.