Currently MacOS Sequoia 15.0.0 is supported by Encryption 12.X versions.
Support for MacOS Sequoia 15.0.0 has been certified starting with SEE 12.0. Please refer to the below documentation for more information:
https://techdocs.broadcom.com/us/en/symantec-security-software/information-security/encryption/12-0-0/sys-req-home-page/see-client-sys-req.html